Logo
Alpher Online
 Current page : Home

301 Moved Permanently

Moved Permanently

The document has moved here.


Apache Server at killexams.com Port 80
Pass4sure 000-634 Practice Test | IBM 000-634 Latest Questions Answers and Pass4sure cheat sheets - alphernet.com.au

000-634 | Object Oriented Analysis and Design - Part 2

Updated 000-634 Practice Test @ Killexams

Complete Practice Exam is provided Here   |   View Blog Article Home

000-634 - Object Oriented Analysis and Design - Part 2 - braindump

Vendor IBM
Exam Number 000-634
Exam Name Object Oriented Analysis and Design - Part 2
Questions 72 Q & A
Recent Update February 14, 2019
Free PDF Download 000-634 Brain Dump
Download Complete PDF Killexams 000-634 Complete Document


Dont Miss these IBM 000-634 Dumps


The best way to get achievement in the IBM 000-634 exam is that you ought to acquire dependable preliminary materials. We guarantee that killexams.com is the most direct pathway toward Implementing IBM Object Oriented Analysis and Design - Part 2 exam. You will be triumphant with full certainty. You can see free questions at killexams.com before you purchase the 000-634 exam items. Our reenacted tests are the same As the real exam design. The questions and answers made by the ensured experts. They give you the experience of stepping through the real exam. 100% guarantee to pass the 000-634 actual test.

killexams.com IBM Certification study guides are setup by IT experts. Heaps of understudies have been griping that an excessive number of questions in such a large number of practice exams and study aides, and they are simply worn out to bear the cost of any more. Seeing killexams.com specialists work out this thorough adaptation while still guarantee that all the information is secured after profound research and investigation. Everything is to make comfort for applicants on their street to certification.

We have Tested and Approved 000-634 Exams. killexams.com gives the most exact and latest IT exam materials which nearly contain all information focuses. With the guide of our 000-634 study materials, you don't need to squander your chance on perusing greater part of reference books and simply need to burn through 10-20 hours to ace our 000-634 real questions and answers. What's more, we give you PDF Version and Software Version exam questions and answers. For Software Version materials, Its offered to give the hopefuls recreate the IBM 000-634 exam in a real domain.

We give free update. Inside legitimacy period, if 000-634 brain dumps that you have bought updated, we will illuminate you by email to download latest rendition of Q&A. On the off chance that you don't pass your IBM Object Oriented Analysis and Design - Part 2 exam, We will give you full refund. You have to send the verified duplicate of your 000-634 exam report card to us. after affirming, we will give you FULL REFUND.

killexams.com Huge Discount Coupons and Promo Codes are as under;
WC2017: 60% Discount Coupon for all exams on website
PROF17: 10% Discount Coupon for Orders greater than $69
DEAL17: 15% Discount Coupon for Orders greater than $99
DECSPECIAL: 10% Special Discount Coupon for All Orders


if you get ready for the IBM 000-634 exam utilizing our testing engine. It is anything but difficult to prevail for all certifications in the first attempt. You don't need to manage all dumps or any free deluge/rapidshare all stuff. We offer free demo of every Certification Dumps. You can look at the interface, question quality and ease of use of our practice exams before you choose to purchase.


000-634 dumps, 000-634 Discount Coupon, 000-634 Promo Code, 000-634 vce, Free 000-634 vce, Download Free 000-634 dumps, Free 000-634 brain dumps, pass4sure 000-634, 000-634 practice test, 000-634 practice exam, killexams.com 000-634, 000-634 real questions, 000-634 actual test, 000-634 PDF download, Pass4sure 000-634 Download, 000-634 help, 000-634 examcollection, Passleader 000-634, exam-labs 000-634, Justcertify 000-634, certqueen 000-634, 000-634 testking


View Full Exam »

Customer Reviews about 000-634

Testimonials Here   |   View Vendors, Tracks Home

000-634 - Object Oriented Analysis and Design - Part 2 - Reviews

Our customers are always happy to give their reviews about the exams. Most of them are our permanent users. They do not rely on others except our team and they get exam confidence by using our questions and answers and exam simulator.

Very clean to get certified in 000-634 exam with this have a look at manual.

Hurrah! i have passed my 000-634 this week. and i got flying coloration and for all this i am so thankful to Killexams. they havegive you so splendid and well-engineered software. Their simulations are very just like the ones in real test. Simulations are the primary factor of 000-634 exam and well worth extra weight age then different questions. After preparingfrom their application it turned into very clean for me to resolve all the ones simulations. I used them for all 000-634 exam and found them trustful on every occasion.

Get those 000-634 real exam questions and solutions! Do now not get rippoff

i am ranked very high amongst my elegance buddies at the list of brilliant students but it best took place once I registered on this Killexams for some exam assist. It was the excessive marks analyzing software on this Killexams that helped me in becoming a member of the high ranks along with different splendid students of my class. The sources on this Killexams are commendable due to the fact theyre specific and extraordinarily beneficial for instruction thru 000-634 pdf, 000-634 dumps and 000-634 books. I am glad to jot down these words of appreciation due to the fact this Killexams deserves it. thank you.

Is there a shortcut to clear 000-634 exam?

I organized the 000-634 exam with the help of Killexams 000-634 check preparation material. It changed into complicated but common very useful in passing my 000-634 exam.

Real 000-634 questions and brain dumps! It justify the price.

Being an below common pupil, I got terrified of the 000-634 exam as subjects looked very tough to me. But passing the test was a need as I needed to exchange the activity badly. Searched for an smooth manual and got one with the dumps. It helped me answer all a couple of type questions in two hundred mins and pass safely. What an superb question & solutions, braindumps! Happy to acquire gives from well-known corporations with good-looking package. I endorse best Killexams

Check out these real 000-634 questions and study help.

I am not a fan of online brain dumps, because they are often posted by irresponsible people who mislead you into learning stuff you dont need and missing things that you really need to know. Not Killexams. This company provides absolutely valid questions answers that help you get through your exam preparation. This is how I passed 000-634 exam. First time, First I relied on free online stuff and I failed. I got Killexams 000-634 exam simulator - and I passed. This is the only proof I need. Thanks Killexams.

I need Latest dumps of 000-634 exam.

I have been using the Killexams for a while to all my exams. Last week, I passed with a great score in the 000-634 exam by using the Q&A study resources. I had some doubts on topics, but the material cleared all my doubts. I have easily found the solution for all my doubts and issues. Thanks for providing me the solid and reliable material. It is the best product as I know.

Little observe for 000-634 examination, first rate success.

It had been years and I was caught on the identical designation, it became like being glued to the chair with fevicol. Initially you observed, just wait right things are available time. But then your persistence wears off and you realize you gotta take a stand before its too past due. Since my work includes primarily managing a 000-634 shoppers base I determined to ace it and end up the he is aware of all approximately 000-634 dude within the office. Upon a buddies steerage I attempted your 000-634 demo from Killexams, loved and it and moved onto a purchase. Your exam simulator is terrifi and nowadays your test package has made me the brand new 000-634 manager.

got no issue! 24 hours prep of 000-634 actual take a look at questions is sufficient.

in case you want to exchange your destiny and ensure that happiness is your destiny, you want to work hard. opemarkstough on my own isnt sufficient to get to future, you want a few route in order to lead you toward the path. It wasdestiny that i found this Killexams all through my exams because it lead me towards my destiny. My fate changed into getting accurate grades and this Killexams and its teachers made it feasible my coaching we so well that I couldnt in all likelihood fail by way of giving me the material for my 000-634 exam.

000-634 question bank that works!

Killexams is the high-quality and correct manner i have ever encounter to prepare and pass IT checks. The factor is, it offers you appropriately and exactly what you want to realise for 000-634 exam. My pals used Killexams for Cisco, Oracle, Microsoft, ISC and different certifications, all exact and legitimate. Absolutely dependable, my private desired.

it's miles sincerely excellent experience to have 000-634 brand new dumps.

I must admit, I was at my wits end and knew after failing the 000-634 test the first time that I was on my own. Until I searched the web for my test. Many sites had the sample help exams and some for around $200. I found this site and it was the lowest price around and I really could not afford it but bit the bullet and purchased it here. I know I sound like a Salesman for this company but I cannot believe that I passed my cert exam with a 98!!!!!! I opened the exam only to see almost every question on it was covered in this sample! You guys rock big time! If you need me, call me for a testimonial cuz this works folks!

Review Complete Testimonials »

See more IBM exam dumps

Direct Downloads Here   |   View Vendors, Latest Home

Real Exam Questions and Answers of exams

We offer a huge collection of IBM exam questions and answers, study guides, practice exams, Exam Simulator.

C2180-277 | A2030-280 | C2150-202 | 000-N23 | 000-700 | C2010-658 | A2090-312 | C2080-471 | C4040-129 | 000-730 | 000-340 | COG-632 | 000-564 | LOT-916 | 000-151 | 000-M98 | C2180-319 | A2040-985 | 000-141 | 000-879 | C2090-632 | A2030-283 | 000-M249 | C2120-800 | 000-N04 | C2070-582 | C2090-136 | C2070-981 | P2060-001 | 000-M235 | 000-M246 | A2040-403 | 000-891 | C4040-252 | A2040-956 | P8060-017 | C2090-549 | C2010-576 | 000-M93 | C2030-284 | C2090-102 | C4040-227 | 000-573 | LOT-913 | 000-N09 | 000-834 | 000-585 | A2040-928 | M2090-234 | C2010-597 |

View Complete IBM Collection »

Latest Exams added

Recently Updated Here   |   View Vendors, Latest Home

Latest Practice Exam Questions and Answers Added to Killexams.com

We keep our visitors and customers updated regarding the latest technology certifications by providing reliable and authentic exam preparation material. Our team remain busy in updating 000-634 exam training material as well as reviewing the real exam changes. They try best to provide each and every relevant information about the test for the candidate to get good marks and come out of test center happily.

1Y0-340 | 1Z0-324 | 1Z0-344 | 1Z0-346 | 1Z0-813 | 1Z0-900 | 1Z0-935 | 1Z0-950 | 1Z0-967 | 1Z0-973 | 1Z0-987 | A2040-404 | A2040-918 | AZ-101 | AZ-102 | AZ-200 | AZ-300 | AZ-301 | FortiSandbox | HP2-H65 | HP2-H67 | HPE0-J57 | HPE6-A47 | JN0-662 | MB6-898 | ML0-320 | NS0-159 | NS0-181 | NS0-513 | PEGACPBA73V1 | 1Z0-628 | 1Z0-934 | 1Z0-974 | 1Z0-986 | 202-450 | 500-325 | 70-537 | 70-703 | 98-383 | 9A0-411 | AZ-100 | C2010-530 | C2210-422 | C5050-380 | C9550-413 | C9560-517 | CV0-002 | DES-1721 | MB2-719 | PT0-001 | CPA-REG | CPA-AUD | AACN-CMC | AAMA-CMA | ABEM-EMC | ACF-CCP | ACNP | ACSM-GEI | AEMT | AHIMA-CCS | ANCC-CVNC | ANCC-MSN | ANP-BC | APMLE | AXELOS-MSP | BCNS-CNS | BMAT | CCI | CCN | CCP | CDCA-ADEX | CDM | CFSW | CGRN | CNSC | COMLEX-USA | CPCE | CPM | CRNE | CVPM | DAT | DHORT | CBCP | DSST-HRM | DTR | ESPA-EST | FNS | FSMC | GPTS | IBCLC | IFSEA-CFM | LCAC | LCDC | MHAP | MSNCB | NAPLEX | NBCC-NCC | NBDE-I | NBDE-II | NCCT-ICS | NCCT-TSC | NCEES-FE | NCEES-PE | NCIDQ-CID | NCMA-CMA | NCPT | NE-BC | NNAAP-NA | NRA-FPM | NREMT-NRP | NREMT-PTE | NSCA-CPT | OCS | PACE | PANRE | PCCE | PCCN | PET | RDN | TEAS-N | VACC | WHNP | WPT-R | 156-215-80 | 1D0-621 | 1Y0-402 | 1Z0-545 | 1Z0-581 | 1Z0-853 | 250-430 | 2V0-761 | 700-551 | 700-901 | 7765X | A2040-910 | A2040-921 | C2010-825 | C2070-582 | C5050-384 | CDCS-001 | CFR-210 | NBSTSA-CST | E20-575 | HCE-5420 | HP2-H62 | HPE6-A42 | HQT-4210 | IAHCSMM-CRCST | LEED-GA | MB2-877 | MBLEX | NCIDQ | VCS-316 | 156-915-80 | 1Z0-414 | 1Z0-439 | 1Z0-447 | 1Z0-968 | 300-100 | 3V0-624 | 500-301 | 500-551 | 70-745 | 70-779 | 700-020 | 700-265 | 810-440 | 98-381 | 98-382 | 9A0-410 | CAS-003 | E20-585 | HCE-5710 | HPE2-K42 | HPE2-K43 | HPE2-K44 | HPE2-T34 | MB6-896 | VCS-256 | 1V0-701 | 1Z0-932 | 201-450 | 2VB-602 | 500-651 | 500-701 | 70-705 | 7391X | 7491X | BCB-Analyst | C2090-320 | C2150-609 | IIAP-CAP | CAT-340 | CCC | CPAT | CPFA | APA-CPP | CPT | CSWIP | Firefighter | FTCE | HPE0-J78 | HPE0-S52 | HPE2-E55 | HPE2-E69 | ITEC-Massage | JN0-210 | MB6-897 | N10-007 | PCNSE | VCS-274 | VCS-275 | VCS-413 |

View Complete List »

See more braindumps

Direct Downloads Here   |   View Vendors, Latest Home

Actual Test Questions and Answers of exams

Here are some exams that you can explore by clicking the link below. There are thousands of exams that we provide to our candidates covering almost all the areas of certifications. Prepare our Questions and Answers and you will Pass4sure.

HP2-W103 | HP3-C36 | P2090-045 | 000-590 | COG-400 | 2B0-100 | 000-005 | 920-172 | 1Y0-264 | 301b | 000-070 | 00M-605 | 412-79 | HP3-X02 | 132-S-911.3 | HP2-H27 | 70-505-CSharp | 6001-1 | 000-M43 | 000-150 | C2090-312 | A2180-529 | 312-49 | 9L0-407 | 190-823 | HP2-B29 | 156-310 | HP3-C27 | IC3-3 | MB4-212 | 920-807 | C2180-278 | 2B0-018 | 0B0-106 | P9510-020 | 000-397 | 1Z0-327 | ST0-052 | LOT-440 | 1Z0-447 | HP5-B05D | 920-548 | HP0-M41 | 4H0-712 | CSM-001 | 000-397 | JN0-330 | VCS-371 | HP0-M54 | HP2-Z17 |

Read more Details »

Top of the list Vendors

Certification Vendors Here   |   View Exams, Latest Home

Industry Leading Vendors

Top notch vendors that dominate the entire world market by their technology and experties. We try to cover almost all the technology vendors and their certification areas so that our customers and visitors obtain all the information about test at one place.

Avaya | NCLEX | ACT | CWNP | Intel | Informatica | Siemens | SANS | CIW | The-Open-Group | IQN | TIA | Veeam | PTCB | Hyperion | ICDL | Nortel | mySQL | Genesys | Financial | LSI | IAHCSMM | Brocade | Esri | Legato | Admission-Tests | Aruba | Magento | Autodesk | QAI | ECCouncil | SUSE | EMC | FSMTB | Exin | Cognos | Prince2 | Certiport | Tibco | GAQM | TruSecure | ISEB | IRS | Altiris | Business-Tests | Worldatwork | Real Estate | IEEE | Fortinet | SASInstitute |

View Complete List »

000-634 Sample Questions

Certification Vendors Here   |   View Exams, Latest Home

000-634 Demo and Sample

Note: Answers are below each question.
Samples are taken from full version.

Pass4sure 000-634 dumps | Killexams.com 000-634 real questions | [HOSTED-SITE]



Killexams.com 000-634 Dumps and Real Questions

100% Real Questions - Exam Pass Guarantee with High Marks - Just Memorize the Answers



000-634 exam Dumps Source : Object Oriented Analysis and Design - Part 2

Test Code : 000-634
Test Name : Object Oriented Analysis and Design - Part 2
Vendor Name : IBM
Q&A : 72 Real Questions

the way to prepare for 000-634 exam in shortest time?
I would absolutely propose killexams.com to every person whos giving 000-634 exam as this no longer honestly facilitates to sweep up the principles within the workbook however additionally offers a top notch idea about the pattern of questions. Remarkableassist ..For the 000-634 exam. Thank you lots killexams.com team !


amazed to see 000-634 dumps and have a look at manual!
Nowadays im very satisfied because i have were given a totally excessive score in my 000-634 exam. I couldnt assume i would be able to do it but this killexams.com made me count on otherwise. The net educators are doing their procedure thoroughly and that i salute them for their determination and devotion.


it is unbelieveable questions for 000-634 test.
Hurrah! I have passed my 000-634 this week. And i got flying shade and for all this i am so grateful to killexams. Theyvegive you so wonderful and nicely-engineered software program. Their simulations are very much like the ones in actual exams. Simulations are the number one factor of 000-634 exam and rightly well worth more weight age then distinct questions. After preparingfrom their software it become very easy for me to resolve all the ones simulations. I used them for all 000-634 exam and discovered them trustful on every occasion.


it's far genuinely superb revel in to have 000-634 real take a look at questions.
It became the time whilst i was scanning for the internet exam simulator, to take my 000-634 exam. I solved all questions in just ninety minutes. It become extraordinary to recognize that killexams.com Questions & solutions had all important dump that become wished for the exam. The material of killexams.com changed into powerful to the pointthat I passed my exam. whilst i was instructed about killexams.com Questions & answers with the aid of one of my partners, i was hesitant to utilize it so I selected to download the demos to begin with, and test whether i canget right help for the 000-634 exam.


it's miles brilliant perfect to prepare 000-634 exam with actual test questions.
Like many others, i have currently handed the 000-634 exam. In my case, sizable majority of 000-634 exam questions got hereexactly from this manual. The solutions are correct, too, so if you are preparing to take your 000-634 exam, you cancompletely depend upon this internet site.


Very easy to get licensed in 000-634 examination with this examine guide.
I have passed the 000-634 exam with this! This is the first time I used killexams.com, but now I know its not gonna be the last one! With the practice exams and real questions, taking this exam was surprisingly easy. This is a great way to get certified - which are nothing like anything else. If youve been through any of their exams, youll know what I mean. 000-634 is hard, but killexams.com is a blessing!


Do you need dumps latest 000-634 examination to pass the examination?
I should admit, choosing killexams.com become the subsequent smart decision I took after deciding on the 000-634 exam. The styles and questions are so rightly unfold which lets in person enhance their bar by the time they attain the closing simulation exam. Appreciate the efforts and honest thanks for supporting pass the exam. Keep up the good work. Thanks killexams.


wherein can i am getting understanding of 000-634 exam?
I am very happy with this bundle deal as I were given over 96% in this 000-634 exam. I read the reliable 000-634 manual a bit, but I guess killexams.com was my important schooling useful resource. I memorized maximum of the questions and answers, and additionally invested the time to simply understand the situations and tech/practice targeted elements of the exam. I count on that via itself buying the killexams.com bundle does now not assure that you will pass your exam - and some tests are sincerely hard. Yet, in case you test their material difficult and definitely positioned your brain and your heart into your exam guidance, then killexams.com truly beats any other exam prep alternatives to be had accessible.


wherein to register for 000-634 examination?
I wanted to have certification in Test 000-634 and i am getting it with killexams. Perfect pattern of latest modules facilitate me to strive all the 38 questions in the given timeframe. I marks more than 87. I should say that I could in no way ever have done it on my own what I became capable of obtain with killexams.com Q&A. killexams.com Q&A provide the cutting-edge module of questions and cowl the related topics. Thanks to killexams.com Q&A.


it's miles incredible ideal to put together 000-634 exam with ultra-modern dumps.
The killexams.com dump is straightforward to understand and enough to prepare for the 000-634 exam. No other observe material I used alongside aspect the Dumps. My heartfelt manner to you for developing such an notably powerful, simple material for the hardexam. I in no way notion I must pass this exam with out difficulty with none tries. You humans made it take vicinity. I responded 76 questions most correctly in the real exam. Thank you for imparting me an contemporary product.


IBM Object Oriented Analysis and

Object-Oriented analysis and Design | killexams.com Real Questions and Pass4sure dumps

This chapter is from the ebook 

analysis emphasizes an investigation of the issue and necessities, instead of a solution. for instance, if a new online buying and selling equipment is preferred, how will or not it's used? What are its functions?

"evaluation" is a extensive term, most reliable qualified, as in requirements analysis (an investigation of the necessities) or object-oriented evaluation (an investigation of the domain objects).

Design emphasizes a conceptual answer (in utility and hardware) that fulfills the requirements, rather than its implementation. as an instance, an outline of a database schema and software objects. Design concepts frequently exclude low-degree or "obtrusive" particulars—glaring to the meant patrons. in the end, designs can also be carried out, and the implementation (similar to code) expresses the real and comprehensive realized design.

As with analysis, the term is optimal certified, as in object-oriented design or database design.

useful evaluation and design had been summarized within the phrase do the appropriate thing (evaluation), and do the issue appropriate (design).


Object-Oriented evaluation And Design — Introduction (half 1) | killexams.com Real Questions and Pass4sure dumps

The thought Of Object-Orientation

Object-orientation is what’s called a programming paradigm. It’s not a language itself but a group of concepts this is supported through many languages.

if you aren’t everyday with the concepts of object-orientation, you may take a glance on the Story of Object-Oriented Programming.

If everything we do in these languages is object-oriented, it skill, we are oriented or concentrated around objects.

Now in an object-oriented language, this one big software will as a substitute be split aside into self contained objects, practically like having a few mini-programs, each object representing a distinct a part of the software.

and each object incorporates its personal records and its personal logic, and they talk between themselves.

These objects aren’t random. They represent the style you talk and think in regards to the difficulty you try to resolve on your real lifestyles.

They symbolize issues like personnel, photos, financial institution debts, spaceships, asteroids, video phase, audio files, or whatever thing exists to your program.

Object-Oriented analysis And Design (OOAD)

It’s a structured formula for analyzing, designing a system by way of making use of the thing-orientated concepts, and develop a group of graphical equipment models throughout the building lifestyles cycle of the application.

OOAD in the SDLC

The application life cycle is customarily divided up into degrees going from summary descriptions of the difficulty to designs then to code and checking out and eventually to deployment.

The earliest tiers of this technique are evaluation (requirements) and design.

The big difference between analysis and design is often described as “what Vs how”.

In analysis builders work with users and domain consultants to outline what the system is meant to do. Implementation details are speculated to be more often than not or absolutely unnoticed at this part.

The goal of the evaluation section is to create a model of the device inspite of constraints reminiscent of acceptable expertise. here's typically performed via use cases and summary definition of probably the most essential objects the use of conceptual model.

The design phase refines the analysis mannequin and applies the crucial know-how and different implementation constrains.

It focuses on describing the objects, their attributes, behavior, and interactions. The design mannequin should still have the entire particulars required in order that programmers can put into effect the design in code.

They’re most excellent conducted in an iterative and incremental utility methodologies. So, the actions of OOAD and the developed fashions aren’t done as soon as, we are able to revisit and refine these steps perpetually.

Object-Oriented evaluation

within the object-oriented analysis, we …

  • Elicit necessities: define what does the application deserve to do, and what’s the difficulty the utility attempting to resolve.
  • Specify requirements: Describe the necessities, usually, the use of use circumstances (and eventualities) or consumer reports.
  • Conceptual mannequin: identify the critical objects, refine them, and define their relationships and behavior and draw them in a simple diagram.
  • We’re now not going to cover the primary two actions, just the final one. These are already defined in aspect in requirements Engineering.

    Object-Oriented Design

    The evaluation part identifies the objects, their relationship, and conduct the usage of the conceptual mannequin (an summary definition for the objects).

    while in design phase, we describe these objects (with the aid of growing type diagram from conceptual diagram — usually mapping conceptual model to classification diagram), their attributes, behavior, and interactions.

    in addition to applying the software design concepts and patterns which could be covered in later tutorials.

    The input for object-oriented design is equipped through the output of object-oriented analysis. however, evaluation and design may additionally ensue in parallel, and the effects of 1 undertaking may also be used with the aid of the different.

    in the object-oriented design, we …

  • Describe the courses and their relationships the use of classification diagram.
  • Describe the interplay between the objects the usage of sequence diagram.
  • follow application design ideas and design patterns.
  • a category diagram gives a visual illustration of the courses you want. And right here is where you get to be in fact particular about object-oriented principles like inheritance and polymorphism.

    Describing the interactions between those objects permits you to greater understand the duties of the distinctive objects, the behaviors they should have.

    — other diagrams

    there are many other diagrams we are able to use to mannequin the equipment from diverse perspectives; interactions between objects, constitution of the gadget, or the behavior of the system and how it responds to activities.

    It’s always about deciding on the correct diagram for the correct want. you should realize which diagrams can be constructive when brooding about or discussing a circumstance that isn’t clear.

    device modeling and the distinctive fashions we will use will be mentioned subsequent.

    equipment Modeling

    gadget modeling is the procedure of constructing fashions of the system, with each and every model representing a distinct perspectives of that device.

    essentially the most essential element about a equipment model is that it leaves out element; It’s an summary illustration of the device.

    The fashions are always based on graphical notation, which is almost always in accordance with the notations within the Unified Modeling Language (UML). different fashions of the gadget like mathematical mannequin; an in depth system description.

    models are used during the evaluation technique to assist to elicit the requirements, right through the design technique to describe the device to engineers, and after implementation to document the gadget structure and operation.

    different views

    We can also develop a mannequin to signify the device from different views.

  • exterior, where you mannequin the context or the atmosphere of the device.
  • interplay, where you model the interplay between accessories of a equipment, or between a equipment and different techniques.
  • Structural, the place you model the organization of the device, or the structure of the records being processed by way of the gadget.
  • Behavioral, where you model the dynamic behavior of the device and the way it reply to pursuits.
  • Unified Modeling Language (UML)

    The unified modeling language become the normal modeling language for object-oriented modeling. It has many diagrams, youngsters, the most diagrams that are widely used are:

  • Use case diagram: It indicates the interplay between a equipment and it’s ambiance (users or programs) within a selected condition.
  • type diagram: It shows the distinct objects, their relationship, their behaviors, and attributes.
  • Sequence diagram: It indicates the interactions between the diverse objects in the device, and between actors and the objects in a equipment.
  • State desktop diagram: It indicates how the equipment respond to external and interior activities.
  • exercise diagram: It shows the stream of the information between the techniques within the system.
  • which you can do diagramming work on paper or on a whiteboard, as a minimum within the initial stages of a venture. however there are some diagramming tools on the way to aid you to draw these UML diagrams.


    document: IBM Outpaces opponents in utility construction application market for Seventh Straight yr | killexams.com Real Questions and Pass4sure dumps

    source: IBM

    June 13, 2008 08:00 ET

    ARMONK, new york--(Marketwire - June 13, 2008) - IBM (NYSE: IBM) nowadays introduced that analyst firm Gartner, Inc.* and market research company Evans facts Corp. have ranked IBM as the chief in the software development application market. These rankings come just as IBM is projecting more than 12,000 people will attend its 2008 IBM Rational utility construction Conferences in 13 nations all over the world.

    Gartner named IBM the worldwide market share chief in utility construction in line with complete software profits in 2007 and Evans statistics Corp. survey respondents who were users of IBM Rational application Developer ranked it the number one built-in Developer atmosphere (IDE) for person delight. here's the seventh consecutive 12 months that Gartner has ranked IBM the chief and 2d consecutive yr that IBM Rational software Developer became selected as the Developer's choice desirable IDE via the 1,200 builders global collaborating in the survey.

    in line with the impartial Gartner report, IBM is the main market share supplier in complete utility earnings, with 37.eight p.c market share -- improved market share than its three closest opponents combined. The global utility development software market grew greater than 10% p.c in 2007 to practically $6.9 billion, according to Gartner.

    IBM became additionally noted for its typical management in accordance with complete software salary for 2007 across application building market sub-classes, including SCCM distributed, Object Oriented analysis & Design and Java Platform advert device. Telelogic, currently received by using IBM, had a 2007 marketshare of forty.6 percent in the requirements Elicitation and administration class according to total software salary.

    "With the rise of worldwide allotted application development groups, clients are trying to find skilled carriers to support them collaborate in an open and clear manner," talked about Dr. Daniel Sabbah, normal manager, IBM Rational software. "We believe the robust response from the Evans facts and Gartner reports coincides with the remarks we've received from shoppers about IBM's strategy around advantageous application beginning."

    IBM Kicks off the realm's Most Attended Developer convention collection

    This marketshare news coincides with IBM's announcement that over 12,000 participants are expected to attend the 15 IBM Rational application building Conferences planned all over. Following the event held last week in Orlando, FL, IBM will take the demonstrate on the highway to 17 cities including Sharm El Sheikh, Egypt; San Paulo, Brazil; Bangalore, India; Shanghai, China; Rome and Milan, Italy.

    For conference attendees using an iPhone, IBM is releasing a convention scheduler written in enterprise era Language (EGL) to permit iPhone clients to dynamically adventure the IBM Rational software building conference via an interface that they suppose comfy with. the usage of internet 2.0 and social engineering ideas, clients can give comments on and chat about classes, navigate the conference searching for tracks and pursuits, and use artistic technology that implies which talks the consumer should still attend next in response to preferences.

    on the annual IBM Rational application construction convention in Orlando, Florida, greater than three,500 attendees discovered about new software and programs that assist clients seriously change how they are birth software on a world scale. The announcement of latest items, functions and business partner initiatives are designed to seriously change how IBM Rational software can aid consumers drive more advantageous price and efficiency from their globally disbursed software investments.

    purchasers unable to attend the convention in the community can view the keynote shows on IBM tv.

    IBM helps builders stay competitive in state-of-the-art quickly-paced development ambiance. ingenious programs comparable to IBM developerWorks, the premier technical resource for software developers, and IBM alphaWorks, IBM's emerging applied sciences outlet, supply an internet neighborhood for the developers of nowadays and tomorrow. builders who are unbiased application carriers can take skills of income and marketing tools, skill-constructing courses and technical help by joining the international IBM PartnerWorld software. IBM's academic Initiative and IBM Rational application development convention are examples of the continuing researching and group-constructing classes crucial by way of students, educators and developers worldwide.

    For greater assistance, consult with http://www.ibm.com/application/rational.

    *"Market Share: application construction software, worldwide, 2007" by using Laurie Wurster, Teresa Jones and Asheesh Raina, may additionally 2008.


    Obviously it is hard assignment to pick solid certification questions/answers assets concerning review, reputation and validity since individuals get sham because of picking incorrectly benefit. Killexams.com ensure to serve its customers best to its assets concerning exam dumps update and validity. The vast majority of other's sham report objection customers come to us for the brain dumps and pass their exams cheerfully and effectively. We never trade off on our review, reputation and quality because killexams review, killexams reputation and killexams customer certainty is vital to us. Uniquely we deal with killexams.com review, killexams.com reputation, killexams.com sham report grievance, killexams.com trust, killexams.com validity, killexams.com report and killexams.com scam. In the event that you see any false report posted by our rivals with the name killexams sham report grievance web, killexams.com sham report, killexams.com scam, killexams.com dissension or something like this, simply remember there are constantly terrible individuals harming reputation of good administrations because of their advantages. There are a great many fulfilled clients that pass their exams utilizing killexams.com brain dumps, killexams PDF questions, killexams hone questions, killexams exam simulator. Visit Killexams.com, our specimen questions and test brain dumps, our exam simulator and you will realize that killexams.com is the best brain dumps site.

    [OPTIONAL-CONTENTS-2]


    70-741 test prep | HP2-K41 exam prep | 1Z0-333 study guide | 2V0-620 free pdf | ST0-47X questions and answers | C2020-701 real questions | C5050-062 free pdf | 310-878 dumps questions | 000-N27 braindumps | 642-270 dumps | 000-266 questions and answers | ITIL-F mock exam | 202-400 questions answers | C2020-625 braindumps | CSET dump | 000-798 practice questions | F50-533 Practice test | HP2-E41 cram | 1Z0-593 braindumps | 101-400 bootcamp |


    Free killexams.com 000-634 question bank
    Just go through our Questions bank and feel confident about the 000-634 test. You will pass your exam at high marks or your money back. Everything you need to pass the 000-634 exam is provided here. We have aggregated a database of 000-634 Dumps taken from real exams so as to give you a chance to get ready and pass 000-634 exam on the very first attempt. Simply set up our Exam Simulator and get ready. You will pass the exam.

    Are you looking for Pass4sure IBM 000-634 Dumps containing real exams questions and answers for the Object Oriented Analysis and Design - Part 2 Exam prep? We provide most updated and quality source of 000-634 Dumps that is http://killexams.com/pass4sure/exam-detail/000-634. We have compiled a database of 000-634 Dumps questions from actual exams in order to let you prepare and pass 000-634 exam on the first attempt. killexams.com Huge Discount Coupons and Promo Codes are as under;
    WC2017 : 60% Discount Coupon for all exams on website
    PROF17 : 10% Discount Coupon for Orders greater than $69
    DEAL17 : 15% Discount Coupon for Orders greater than $99
    DECSPECIAL : 10% Special Discount Coupon for All Orders

    The best way to get success in the IBM 000-634 exam is that you ought to attain reliable preparatory materials. We guarantee that killexams.com is the maximum direct pathway closer to Implementing IBM Object Oriented Analysis and Design - Part 2 certificate. You can be successful with full self belief. You can view free questions at killexams.com earlier than you purchase the 000-634 exam products. Our simulated assessments are in a couple of-choice similar to the actual exam pattern. The questions and answers created by the certified experts. They offer you with the enjoy of taking the real exam. 100% assure to pass the 000-634 actual test.

    killexams.com IBM Certification exam courses are setup by way of IT specialists. Lots of college students have been complaining that there are too many questions in such a lot of exercise tests and exam courses, and they're just worn-out to find the money for any greater. Seeing killexams.com professionals training session this complete version at the same time as nonetheless guarantee that each one the information is included after deep research and evaluation. Everything is to make convenience for candidates on their road to certification.

    We have Tested and Approved 000-634 Exams. killexams.com provides the most correct and latest IT exam materials which nearly contain all information references. With the aid of our 000-634 exam materials, you dont need to waste your time on studying bulk of reference books and simply want to spend 10-20 hours to master our 000-634 actual questions and answers. And we provide you with PDF Version & Software Version exam questions and answers. For Software Version materials, Its presented to provide the applicants simulate the IBM 000-634 exam in a real environment.

    We offer free replace. Within validity length, if 000-634 exam materials that you have purchased updated, we will inform you with the aid of email to down load state-of-the-art model of Q&A. If you dont pass your IBM Object Oriented Analysis and Design - Part 2 exam, We will give you full refund. You want to ship the scanned replica of your 000-634 exam record card to us. After confirming, we will fast provide you with FULL REFUND.

    killexams.com Huge Discount Coupons and Promo Codes are as below;
    WC2017 : 60% Discount Coupon for all exams on website
    PROF17 : 10% Discount Coupon for Orders greater than $69
    DEAL17 : 15% Discount Coupon for Orders more than $ninety nine
    DECSPECIAL : 10% Special Discount Coupon for All Orders


    If you put together for the IBM 000-634 exam the use of our trying out engine. It is simple to succeed for all certifications in the first attempt. You dont must cope with all dumps or any free torrent / rapidshare all stuff. We offer loose demo of every IT Certification Dumps. You can test out the interface, question nice and usability of our exercise assessments before making a decision to buy.

    [OPTIONAL-CONTENTS-4]


    Killexams HP0-M55 braindumps | Killexams HP0-M39 exam prep | Killexams AFE examcollection | Killexams A2010-577 cram | Killexams 1Z0-147 practice test | Killexams C2040-988 test prep | Killexams ICYB Practice test | Killexams HP0-J67 brain dumps | Killexams 00M-243 practice exam | Killexams 9A0-095 mock exam | Killexams C2090-424 real questions | Killexams HP2-E53 free pdf download | Killexams 000-M49 practice questions | Killexams 648-232 braindumps | Killexams HP2-H29 dump | Killexams M2090-626 dumps questions | Killexams 000-M224 real questions | Killexams EC0-349 practice test | Killexams 000-142 Practice Test | Killexams MA0-103 exam questions |


    [OPTIONAL-CONTENTS-5]

    View Complete list of Killexams.com Brain dumps


    Killexams PW0-105 braindumps | Killexams ISSEP practice test | Killexams 190-621 practice questions | Killexams 1Z0-872 VCE | Killexams HPE2-T30 questions and answers | Killexams 70-767 practice exam | Killexams 000-743 cram | Killexams 500-451 cheat sheets | Killexams 650-474 study guide | Killexams 250-505 braindumps | Killexams A2180-181 brain dumps | Killexams 000-R15 free pdf | Killexams 1D0-571 Practice test | Killexams 300-320 study guide | Killexams 000-241 brain dumps | Killexams 156-215-80 bootcamp | Killexams JK0-801 free pdf | Killexams 1Z0-523 questions answers | Killexams LOT-805 test questions | Killexams PDM-2002001060 mock exam |


    Object Oriented Analysis and Design - Part 2

    Pass 4 sure 000-634 dumps | Killexams.com 000-634 real questions | [HOSTED-SITE]

    Object-Oriented Analysis & Design | killexams.com real questions and Pass4sure dumps

    Object-Oriented Analysis & DesignJune 2, 3, 9, 10Worcester State CollegeTaught by Jan Bergandy, Computer Science, UMass, Dartmouth

    Seminar Objectives:

  • To develop an in-depth understanding of object-oriented paradigm
  • To obtain a working knowledge of object-oriented analysis & design techniques
  • To learn object-oriented modeling using Unified Modeling Language (UML)
  • To learn about basic design patterns and the role of patterns is software development
  • To understand the impact of object paradigm on software development activities
  • To explore synergy between object-oriented design and object-oriented programming
  • To learn about key object technologies
  • Who should attend:This workshop is addressed to faculty involved in teaching programming, software design, and other courses related to software development. It is addressed to those who face a transition to object technology and want to learn about challenges and benefits of this transition. The workshop does not require any prior knowledge of object-oriented programming or knowledge of object paradigm. General computer fluency and general knowledge of issues associated with software and software development are expected.

    Seminar Organization:The course will be conducted as a project with instructor giving short presentations pertaining to a specific stage of the analysis and design process. During this course the participants will construct an analysis model for a selected problem. This model will be refined in to the detailed design level providing an opportunity for discussion about the relationship between object-oriented design and object-oriented programming. Each student will receive a copy of the course materials and the textbook.

    Tools & Platforms:Rational-Rose CASE toolThe CASE tool is used exclusively to expedite the process of model construction. The students spend no more than half an hour of their time during the entire class on learning how to use the tool. Not using the CASE toll will make it almost impossible to experience hands-on all the elements of the object-oriented analysis and design process.

    Textbooks:M. Fowler, ÒUML DistilledÓ, Addison-Wesley, ISBN 0-201-32563-2 (additional/optional )

    E. Gamma, R. Helm, R. Johnson, J. Vlissides, ÒDesign PatternÓ, Addison-Wesley, ISBN 0-201-63361-2

    Outline:

    June 2, 2001, 9:00 - 5:00Topics to be addressed:Object paradigm top-down - analysis & design perspectiveObject paradigm bottom-up - programming perspectiveBasic concepts: abstraction, encapsulation, information hiding, modularityResponsibility view of the requirementsClasses and objects emerging from responsibilitiesComparison of procedural and object-oriented paradigmsClasses and relationships as the building blocks of software architectureCriteria of class qualityIntroduction to Unified Modeling Language (UML)Static & dynamic modelActors and use casesTransitioning from functional requirements to objects - introduction

    Project:Analysis of the requirements for the selected projectIdentifying actors and use casesConstructing use case diagrams

    June 3, 2001, 9:00 - 2:00Topics to be addressed:Transitioning from functional requirements to objectsIdentifying the first group of classesClass specificationClass as an encapsulation of a responsibilityClass, Utility Class, Parameterized Class and its instantiationClass diagram - introductionIdentifying relationships between classesAssociation relationshipsAssociation classesRepresenting relationships with cardinalityAggregation versus compositionRepresenting aggregation and composition relationshipsRepresenting generalization/ specialization (inheritance)PolymorphismAbstract classes and interfacesSpecification of relationshipsImplementing classes & relationships (bottom-up view of relationships)Class diagram

    Project:Identifying first group of classes based on responsibilitiesPreliminary class diagramIdentifying relationships between classesDefining cardinalitiesClass diagram

    June 10, 2001, 9:00 - 5:00 (part I)Topics to be addressed:Static versus dynamic modelIdentifying scenarios through refinement of use casesModeling scenarios using object-interaction and sequence diagrams

    Project:Refining use casesDeveloping and modeling scenariosIdentifying methodsRefining class specifications

    June 10, 2001 (part II)Topics to be addressed:Events, states and actionsState diagramCriteria for using state diagramsConcurrency, active objectsMutual exclusion problemSequential, guarded, and synchronous objectsModeling concurrencyConcurrent state diagramsActivity diagrams

    Project:Evaluating classes for the need of state diagramsConstructing state diagrams for selected classes(Constructing activity diagrams)Refining class specifications

    June 10, 2001, 9:00 - 2:00Topics to be addressed:Introduction to design patterns: Creational patterns, Abstract Factory, Builder, Prototype, Singleton, Virtual Constructor

    Structural Patterns: Adapter, Bridge, Composite, Decorator, Façade, Proxy

    Behavioral Patterns: Chain of Responsibility, Command, Iterator, Mediator, Memento

    Other important topics to be covered in this course:What to expect from an object-oriented languageDynamic nature of object-oriented systems and the issues of garbage collectionEffective use of inheritance and polymorphism and their impact on software qualitySingle versus multiple inheritancePolymorphism versus genericsClass design and data normalization (attribute dependence issues)


    Object-oriented design patterns in the kernel, part 2 | killexams.com real questions and Pass4sure dumps

    LWN.net needs you!

    Without subscribers, LWN would simply not exist. Please consider signing up for a subscription and helping to keep LWN publishing

    June 7, 2011

    This article was contributed by Neil Brown

    In the first part of this analysis we looked at how the polymorphic side of object-oriented programming was implemented in the Linux kernel using regular C constructs. In particular we examined method dispatch, looked at the different forms that vtables could take, and the circumstances where separate vtables were eschewed in preference for storing function pointers directly in objects. In this conclusion we will explore a second important aspect of object-oriented programming - inheritance, and in particular data inheritance.

    Data inheritance

    Inheritance is a core concept of object-oriented programming, though it comes in many forms, whether prototype inheritance, mixin inheritance, subtype inheritance, interface inheritance etc., some of which overlap. The form that is of interest when exploring the Linux kernel is most like subtype inheritance, where a concrete or "final" type inherits some data fields from a "virtual" parent type. We will call this "data inheritance" to emphasize the fact that it is the data rather than the behavior that is being inherited.

    Put another way, a number of different implementations of a particular interface share, and separately extend, a common data structure. They can be said to inherit from that data structure. There are three different approaches to this sharing and extending that can be found in the Linux kernel, and all can be seen by exploring the struct inode structure and its history, though they are widely used elsewhere.

    Extension through unions

    The first approach, which is probably the most obvious but also the least flexible, is to declare a union as one element of the common structure and, for each implementation, to declare an entry in that union with extra fields that the particular implementation needs. This approach was introduced to struct inode in Linux-0.97.2 (August 1992) when

    union { struct minix_inode_info minix_i; struct ext_inode_info ext_i; struct msdos_inode_info msdos_i; } u;

    was added to struct inode. Each of these structures remained empty until 0.97.5 when i_data was moved from struct inode to struct ext_inode_info. Over the years several more "inode_info" fields were added for different filesystems, peaking at 28 different "inode_info" structures in 2.4.14.2 when ext3 was added.

    This approach to data inheritance is simple and straightforward, but is also somewhat clumsy. There are two obvious problems. Firstly, every new filesystem implementation needs to add an extra field to the union "u". With 3 fields this may not seem like a problem, with 28 it was well past "ugly". Requiring every filesystem to update this one structure is a barrier to adding filesystems that is unnecessary. Secondly, every inode allocated will be the same size and will be large enough to store the data for any filesystem. So a filesystem that wants lots of space in its "inode_info" structure will impose that space cost on every other filesystem.

    The first of these issues is not an impenetrable barrier as we will see shortly. The second is a real problem and the general ugliness of the design encouraged change. Early in the 2.5 development series this change began; it was completed by 2.5.7 when there were no "inode_info" structures left in union u (though the union itself remained until 2.6.19).

    Embedded structures

    The change that happened to inodes in early 2.5 was effectively an inversion. The change which removed ext3_i from struct inode.u also added a struct inode, called vfs_inode, to struct ext3_inode_info. So instead of the private structure being embedded in the common data structure, the common data structure is now embedded in the private one. This neatly avoids the two problems with unions; now each filesystem needs to only allocate memory to store its own structure without any need to know anything about what other filesystems might need. Of course nothing ever comes for free and this change brought with it other issues that needed to be solved, but the solutions were not costly.

    The first difficulty is the fact that when the common filesystem code - the VFS layer - calls into a specific filesystem it passes a pointer to the common data structure, the struct inode. Using this pointer, the filesystem needs to find a pointer to its own private data structure. An obvious approach is to always place the struct inode at the top of the private inode structure and simply cast a pointer to one into a pointer to the other. While this can work, it lacks any semblance of type safety and makes it harder to arrange fields in the inode to get optimal performance - as some kernel developers are wont to do.

    The solution was to use the list_entry() macro to perform the necessary pointer arithmetic, subtracting from the address of the struct inode its offset in the private data structure and then casting this appropriately. The macro for this was called list_entry() simply because the "list.h lists" implementation was the first to use this pattern of data structure embedding. The list_entry() macro did exactly what was needed and so it was used despite the strange name. This practice lasted until 2.5.28 when a new container_of() macro was added which implemented the same functionality as list_entry(), though with slightly more type safety and a more meaningful name. With container_of() it is a simple matter to map from an embedded data structure to the structure in which it is embedded.

    The second difficulty was that the filesystem had to be responsible for allocating the inode - it could no longer be allocated by common code as the common code did not have enough information to allocate the correct amount of space. This simply involved adding alloc_inode() and destroy_inode() methods to the super_operations structure and calling them as appropriate.

    Void pointers

    As noted earlier, the union pattern was not an impenetrable barrier to adding new filesystems independently. This is because the union u had one more field that was not an "inode_info" structure. A generic pointer field called generic_ip was added in Linux-1.0.5, but it was not used until 1.3.7. Any file system that does not own a structure in struct inode itself could define and allocate a separate structure and link it to the inode through u.generic_ip. This approach addressed both of the problems with unions as no changes are needed to shared declarations and each filesystem only uses the space that it needs. However it again introduced new problems of its own.

    Using generic_ip, each filesystem required two allocations for each inode instead of one and this could lead to more wastage depending on how the structure size was rounded up for allocation; it also required writing more error-handling code. Also there was memory used for the generic_ip pointer and often for a back pointer from the private structure to the common struct inode. Both of these are wasted space compared with the union approach or the embedding approach.

    Worse than this though, an extra memory dereference was needed to access the private structure from the common structure; such dereferences are best avoided. Filesystem code will often need to access both the common and the private structures. This either requires lots of extra memory dereferences, or it requires holding the address of the private structure in a register which increases register pressure. It was largely these concerns that stopped struct inode from ever migrating to broad use of the generic_ip pointer. It was certainly used, but not by the major, high-performance filesystems.

    Though this pattern has problems it is still in wide use. struct super_block has an s_fs_info pointer which serves the same purpose as u.generic_ip (which has since been renamed to i_private when the u union was finally removed - why it was not completely removed is left as an exercise for the reader). This is the only way to store filesystem-private data in a super_block. A simple search in the Linux include files shows quite a collection of fields which are void pointers named "private" or something similar. Many of these are examples of the pattern of extending a data type by using a pointer to a private extension, and most of these could be converted to using the embedded-structure pattern.

    Beyond inodes

    While inodes serve as an effective vehicle to introduce these three patterns they do not display the full scope of any of them so it is useful to look further afield and see what else we can learn.

    A survey of the use of unions elsewhere in the kernel shows that they are widely used though in very different circumstances than in struct inode. The particular aspect of inodes that is missing elsewhere is that a wide range of different modules (different filesystems) each wanted to extend an inode in different ways. In most places where unions are used there are a small fixed number of subtypes of the base type and there is little expectation of more being added. A simple example of this is struct nfs_fattr which stores file attribute information decoded out of an NFS reply. The details of these attributes are slightly different for NFSv2 and NFSv3 so there are effectively two subtypes of this structure with the difference encoded in a union. As NFSv4 uses the same information as NFSv3 this is very unlikely to ever be extended further.

    A very common pattern in other uses of unions in Linux is for encoding messages that are passed around, typically between the kernel and user-space. struct siginfo is used to convey extra information with a signal delivery. Each signal type has a different type of ancillary information, so struct siginfo has a union to encode six different subtypes. union inputArgs appears to be the largest current union with 22 different subtypes. It is used by the "coda" network file system to pass requests between the kernel module and a user-space daemon which handles the network communication.

    It is not clear whether these examples should be considered as the same pattern as the original struct inode. Do they really represent different subtypes of a base type, or is it just one type with internal variants? The Eiffel object-oriented programming language does not support variant types at all except through subtype inheritance so there is clearly a school of thought that would want to treat all usages of union as a form of subtyping. Many other languages, such as C++, provide both inheritance and unions allowing the programmer to make a choice. So the answer is not clear.

    For our purposes it doesn't really matter what we call it as long as we know where to use each pattern. The examples in the kernel fairly clearly show that when all of the variants are understood by a single module, then a union is a very appropriate mechanism for variants structures, whether you want to refer to them as using data inheritance or not. When different subtypes are managed by different modules, or at least widely separate pieces of code, then one of the other mechanisms is preferred. The use of unions for this case has almost completely disappeared with only struct cycx_device remaining as an example of a deprecated pattern.

    Problems with void pointers

    Void pointers are not quite so easy to classify. It would probably be fair to say that void pointers are the modern equivalent of "goto" statements. They can be very useful but they can also lead to very convoluted designs. A particular problem is that when you look at a void pointer, like looking at a goto, you don't really know what it is pointing at. A void pointer called private is even worse - it is like a "goto destination" command - almost meaningless without reading lots of context.

    Examining all the different uses that void pointers can be put to would be well beyond the scope of this article. Instead we will restrict our attention to just one new usage which relates to data inheritance and illustrates how the untamed nature of void pointers makes it hard to recognize their use in data inheritance. The example we will use to explain this usage is struct seq_file used by the seq_file library which makes it easy to synthesize simple text files like some of those in /proc. The "seq" part of seq_file simply indicates that the file contains a sequence of lines corresponding to a sequence of items of information in the kernel, so /proc/mounts is a seq_file which walks through the mount table reporting each mount on a single line.

    When seq_open() is used to create a new seq_file it allocates a struct seq_file and assigns it to the private_data field of the struct file which is being opened. This is a straightforward example of void pointer based data inheritance where the struct file is the base type and the struct seq_file is a simple extension to that type. It is a structure that never exists by itself but is always the private_data for some file. struct seq_file itself has a private field which is a void pointer and it can be used by clients of seq_file to add extra state to the file. For example md_seq_open() allocates a struct mdstat_info structure and attaches it via this private field, using it to meet md's internal needs. Again, this is simple data inheritance following the described pattern.

    However the private field of struct seq_file is used by svc_pool_stats_open() in a subtly but importantly different way. In this case the extra data needed is just a single pointer. So rather than allocating a local data structure to refer to from the private field, svc_pool_stats_open simply stores that pointer directly in the private field itself. This certainly seems like a sensible optimization - performing an allocation to store a single pointer would be a waste - but it highlights exactly the source of confusion that was suggested earlier: that when you look at a void pointer you don't really know what is it pointing at, or why.

    To make it a bit clearer what is happening here, it is helpful to imagine "void *private" as being like a union of every different possible pointer type. If the value that needs to be stored is a pointer, it can be stored in this union following the "unions for data inheritance" pattern. If the value is not a single pointer, then it gets stored in allocated space following the "void pointers for data inheritance" pattern. Thus when we see a void pointer being used it may not be obvious whether it is being used to point to an extension structure for data inheritance, or being used as an extension for data inheritance (or being used as something else altogether).

    To highlight this issue from a slightly different perspective it is instructive to examine struct v4l2_subdev which represents a sub-device in a video4linux device, such as a sensor or camera controller within a webcam. According to the (rather helpful) documentation it is expected that this structure will normally be embedded in a larger structure which contains extra state. However this structure still has not just one but two void pointers, both with names suggesting that they are for private use by subtypes:

    /* pointer to private data */ void *dev_priv; void *host_priv;

    It is common that a v4l sub-device (a sensor, usually) will be realized by, for example, an I2C device (much as a block device which stores your filesystem might be realized by an ATA or SCSI device). To allow for this common occurrence, struct v4l2_subdev provides a void pointer (dev_priv), so that the driver itself doesn't need to define a more specific pointer in the larger structure which struct v4l2_subdev would be embedded in. host_priv is intended to point back to a "parent" device such as a controller which acquires video data from the sensor. Of the three drivers which use this field, one appears to follow that intention while the other two use it to point to an allocated extension structure. So both of these pointers are intended to be used following the "unions for data inheritance" pattern, where a void pointer is playing the role of a union of many other pointer types, but they are not always used that way.

    It is not immediately clear that defining this void pointer in case it is useful is actually a valuable service to provide given that the device driver could easily enough define its own (type safe) pointer in its extension structure. What is clear is that an apparently "private" void pointer can be intended for various qualitatively different uses and, as we have seen in two different circumstances, they may not be used exactly as expected.

    In short, recognizing the "data inheritance through void pointers" pattern is not easy. A fairly deep examination of the code is needed to determine the exact purpose and usage of void pointers.

    A diversion into struct page

    Before we leave unions and void pointers behind a look at struct page may be interesting. This structure uses both of these patterns, though they are hidden somewhat due to historical baggage. This example is particularly instructive because it is one case where struct embedding simply is not an option.

    In Linux memory is divided into pages, and these pages are put to a variety of different uses. Some are in the "page cache" used to store the contents of files. Some are "anonymous pages" holding data used by applications. Some are used as "slabs" and divided into pieces to answer kmalloc() requests. Others are simply part of a multi-page allocation or maybe are on a free list waiting to be used. Each of these different use cases could be seen as a subtype of the general class of "page", and in most cases need some dedicated fields in struct page, such as a struct address_space pointer and index when used in the page cache, or struct kmem_cache and freelist pointers when used as a slab.

    Each page always has the same struct page describing it, so if the effective type of the page is to change - as it must as the demands for different uses of memory change over time - the type of the struct page must change within the lifetime of that structure. While many type systems are designed assuming that the type of an object is immutable, we find here that the kernel has a very real need for type mutability. Both unions and void pointers allow types to change and as noted, struct page uses both.

    At the first level of subtyping there are only a small number of different subtypes as listed above; these are all known to the core memory management code, so a union would be ideal here. Unfortunately struct page has three unions with fields for some subtypes spread over all three, thus hiding the real structure somewhat.

    When the primary subtype in use has the page being used in the page cache, the particular address_space that it belongs to may want to extend the data structure further. For this purpose there is a private field that can be used. However it is not a void pointer but is an unsigned long. Many places in the kernel assume an unsigned long and a void * are the same size and this is one of them. Most users of this field actually store a pointer here and have to cast it back and forth. The "buffer_head" library provides macros attach_page_buffers and page_buffers to set and get this field.

    So while struct page is not the most elegant example, it is an informative example of a case where unions and void pointers are the only option for providing data inheritance.

    The details of structure embedding

    Where structure embedding can be used, and where the list of possible subtypes is not known in advance, it seems to be increasingly the preferred choice. To gain a full understanding of it we will again need to explore a little bit further than inodes and contrast data inheritance with other uses of structure embedding.

    There are essentially three uses for structure embedding - three reasons for including a structure within another structure. Sometimes there is nothing particularly interesting going on. Data items are collected together into structures and structures within structures simply to highlight the closeness of the relationships between the different items. In this case the address of the embedded structure is rarely taken, and it is never mapped back to the containing structure using container_of().

    The second use is the data inheritance embedding that we have already discussed. The third is like it but importantly different. This third use is typified by struct list_head and other structs used as an embedded anchor when creating abstract data types.

    The use of an embedded anchor like struct list_head can be seen as a style of inheritance as the structure containing it "is-a" member of a list by virtue of inheriting from struct list_head. However it is not a strict subtype as a single object can have several struct list_heads embedded - struct inode has six (if we include the similar hlist_node). So it is probably best to think of this sort of embedding more like a "mixin" style of inheritance. The struct list_head provides a service - that of being included in a list - that can be mixed-in to other objects, an arbitrary number of times.

    A key aspect of data inheritance structure embedding that differentiates it from each of the other two is the existence of a reference counter in the inner-most structure. This is an observation that is tied directly to the fact that the Linux kernel uses reference counting as the primary means of lifetime management and so would not be shared by systems that used, for example, garbage collection to manage lifetimes.

    In Linux, every object with an independent existence will have a reference counter, sometimes a simple atomic_t or even an int, though often a more explicit struct kref. When an object is created using several levels of inheritance the reference counter could be buried quite deeply. For example a struct usb_device embeds a struct device which embeds struct kobject which has a struct kref. So usb_device (which might in turn be embedded in a structure for some specific device) does have a reference counter, but it is contained several levels down in the nest of structure embedding. This contrasts quite nicely with a list_head and similar structures. These have no reference counter, have no independent existence and simply provide a service to other data structures.

    Though it seems obvious when put this way, it is useful to remember that a single object cannot have two reference counters - at least not two lifetime reference counters (It is fine to have two counters like s_active and s_count in struct super_block which count different things). This means that multiple inheritance in the "data inheritance" style is not possible. The only form of multiple inheritance that can work is the mixin style used by list_head as mentioned above.

    It also means that, when designing a data structure, it is important to think about lifetime issues and whether this data structure should have its own reference counter or whether it should depend on something else for its lifetime management. That is, whether it is an object in its own right, or simply a service provided to other objects. These issues are not really new and apply equally to void pointer inheritance. However an important difference with void pointers is that it is relatively easy to change your mind later and switch an extension structure to be a fully independent object. Structure embedding requires the discipline of thinking clearly about the problem up front and making the right decision early - a discipline that is worth encouraging.

    The other key telltale for data inheritance structure embedding is the set of rules for allocating and initializing new instances of a structure, as has already been hinted at. When union or void pointer inheritance is used the main structure is usually allocated and initialized by common code (the mid-layer) and then a device specific open() or create() function is called which can optionally allocate and initialize any extension object. By contrast when structure embedding is used the structure needs to be allocated by the lowest level device driver which then initializes its own fields and calls in to common code to initialize the common fields.

    Continuing the struct inode example from above which has an alloc_inode() method in the super_block to request allocation, we find that initialization is provided for with inode_init_once() and inode_init_always() support functions. The first of these is used when the previous use of a piece of memory is unknown, the second is sufficient by itself when we know that the memory was previously used for some other inode. We see this same pattern of an initializer function separate from allocation in kobject_init(), kref_init(), and device_initialize().

    So apart from the obvious embedding of structures, the pattern of "data inheritance through structure embedding" can be recognized by the presence of a reference counter in the innermost structure, by the delegation of structure allocation to the final user of the structure, and by the provision of initializing functions which initialize a previously allocated structure.

    Conclusion

    In exploring the use of method dispatch (last week) and data inheritance (this week) in the Linux kernel we find that while some patterns seem to dominate they are by no means universal. While almost all data inheritance could be implemented using structure embedding, unions provide real value in a few specific cases. Similarly while simple vtables are common, mixin vtables are very important and the ability to delegate methods to a related object can be valuable.

    We also find that there are patterns in use with little to recommend them. Using void pointers for inheritance may have an initial simplicity, but causes longer term wastage, can cause confusion, and could nearly always be replaced by embedded inheritance. Using NULL pointers to indicate default behavior is similarly a poor choice - when the default is important there are better ways to provide for it.

    But maybe the most valuable lesson is that the Linux kernel is not only a useful program to run, it is also a useful document to study. Such study can find elegant practical solutions to real problems, and some less elegant solutions. The willing student can pursue the former to help improve their mind, and pursue the latter to help improve the kernel itself. With that in mind, the following exercises might be of interest to some.

    Exercises
  • As inodes now use structure embedding for inheritance, void pointers should not be necessary. Examine the consequences and wisdom of removing "i_private" from "struct inode".

  • Rearrange the three unions in struct page to just one union so that the enumeration of different subtypes is more explicit.

  • As was noted in the text, struct seq_file can be extended both through "void pointer" and a limited form of "union" data inheritance. Explain how seq_open_private() allows this structure to also be extended through "embedded structure" data inheritance and give an example by converting one usage in the kernel from "void pointer" to "embedded structure". Consider submitting a patch if this appears to be an improvement. Contrast this implementation of embedded structure inheritance with the mechanism used for inodes.

  • Though subtyping is widely used in the kernel, it is not uncommon for a object to contain fields that not all users are interested in. This can indicate that more fine grained subtyping is possible. As very many completely different things can be represented by a "file descriptor", it is likely that struct file could be a candidate for further subtyping.

    Identify the smallest set of fields that could serve as a generic struct file and explore the implications of embedding that in different structures to implement regular files, socket files, event files, and other file types. Exploring more general use of the proposed open() method for inodes might help here.

  • Identify an "object-oriented" language which has an object model that would meet all the needs of the Linux kernel as identified in these two articles.

  • (Log in to post comments)

    Java and Object-Oriented Programming | killexams.com real questions and Pass4sure dumps

    This chapter is from the book 

    Many seasoned Java developers will scoff at the fact that this section even exists in this book. It is here for two very important reasons. The first is that I continually run across Java applications built with a procedural mind-set. The fact that you know Java doesn't mean that you have the ability to transform that knowledge into well-designed object-oriented systems. As both an instructor and consultant, I see many data-processing shops send COBOL and/or Visual Basic developers to a three-day class on UML and a five-day class on Java and expect miracles. Case in point: I was recently asked to review a Java application to assess its design architecture and found that it had only two classes—SystemController and ScreenController—which contained over 70,000 lines of Java code.

    The second reason for the emphasis on how the language maps to object-oriented principles is that people like language comparisons and how they stack up to their counterparts. To appease those that live and die by language comparisons, let's put Java under the scrutiny of what constitutes an object-oriented language.

    No definitive definition of what makes a language object-oriented is globally accepted. However, a common set of criteria I personally find useful is that the language must support the following:

  • Classes
  • Complex types (Java reference types)
  • Message passing
  • Encapsulation
  • Inheritance
  • Polymorphism
  • These are discussed in the next subsections.

    Java and Classes

    Java allows classes to be defined. There are no stray functions floating around in Java. A class is a static template that contains the defined structure (attributes) and behavior (operations) of a real-world entity in the application domain. At runtime, the class is instantiated, or brought to life, as an object born in the image of that class. In my seminars, when several folks new to the object world are in attendance, I often use the analogy of a cookie cutter. The cookie cutter is merely the template used to stamp out what will become individually decorated and unique cookies. The cookie cutter is the class; the unique blue, green, and yellow gingerbread man is the object (which I trust supports a bite operation).

    Java exposes the class to potential outside users through its public interface. A public interface consists of the signatures of the public operations supported by the class. A signature is the operation name and its input parameter types (the return type, if any, is not part of the operation's signature).

    Good programming practice encourages developers to declare all attributes as private and allow access to them only via operations. As with most other languages, however, this is not enforced in Java. Figure 2-1 outlines the concept of a class and its interface.

    FIGURE 2-1 Public interface of a class

    The figure uses a common eggshell metaphor to describe the concept of the class's interface, as well as encapsulation. The internal details of the class are hidden from the outside via a well-defined interface. In this case, only four operations are exposed in the classes interface (Operation_A, B, C, and D). The other attributes and operations are protected from the outside world. Actually, to the outside world, it's as if they don't even exist.

    Suppose you want to create an Order class in Java that has three attributes—orderNumber, orderDate, and orderTotal—and two operations—calcTotalValue() and getInfo(). The class definition could look like this:

    /** * Listing 1 * This is the Order class for the Java/UML book */ package com.jacksonreed; import java.util.*; public class Order { private Date orderDate; private long orderNumber; private long orderTotal; public Order() { } public boolean getInfo() { return true; } public long calcTotalValue() { return 0; } public Date getOrderDate() { return orderDate; } public void setOrderDate(Date aOrderDate) { orderDate = aOrderDate; } public long getOrderNumber() { return orderNumber; } public void setOrderNumber(long aOrderNumber) { orderNumber = aOrderNumber; } public long getOrderTotal() { return orderTotal; } public void setOrderTotal(long aOrderTotal) { orderTotal = aOrderTotal; } public static void main(String[] args) { Order order = new Order(); System.out.println("instantiated Order"); System.out.println(order.getClass().getName()); System.out.println(order.calcTotalValue()); try { Thread.currentThread().sleep(5*1000); } catch(InterruptedException e) {} } }

    A few things are notable about the first bit of Java code presented in this book. Notice that each of the three attributes has a get and a set operation to allow for the retrieval and setting of the Order object's properties. Although doing so is not required, it is common practice to provide these accessor-type operations for all attributes defined in a class. In addition, if the Order class ever wanted to be a JavaBean, it would have to have "getters and setters" defined in this way.

    Some of the method code in the main() operation does a few things of note. Of interest is that a try block exists at the end of the operation that puts the current thread to sleep for a bit. This is to allow the console display to freeze so that you can see the results.

    If you type in this class and then compile it and execute it in your favorite development tool or from the command prompt with

    javac order.java //* to compile it java order //* to run it

    you should get results that look like this:

    instantiated Order com.jacksonreed.Order 0

    NOTE

    Going forward, I promise you will see no code samples with class, operation, or attribute names of foo, bar, or foobar.

    More on Java and Classes

    A class can also have what are called class-level operations and attributes. Java supports these with the static keyword. This keyword would go right after the visibility (public, private, protected) component of the operation or attribute. Static operations and attributes are needed to invoke either a service of the class before any real instances of that class are instantiated or a service that doesn't directly apply to any of the instances. The classic example of a static operation is the Java constructor. The constructor is what is called when an object is created with the New keyword. Perhaps a more business-focused example is an operation that retrieves a list of Customer instances based on particular search criteria.

    A class-level attribute can be used to store information that all instances of that class may access. This attribute might be, for example, a count of the number of objects currently instantiated or a property about Customer that all instances might need to reference.

    Java and Complex Types (Java Reference Types)

    A complex type, which in Java is called a reference type, allows variables typed as something other than primitive types (e.g., int and boolean) to be declared. In Java, these are called reference types. In object-oriented systems, variables that are "of" a particular class, such as Order, Customer, or Invoice, must be defined. Taken a step further, Order could consist of other class instances, such as OrderHeader and OrderLine.

    In Java, you can define different variables that are references to runtime objects of a particular class type:

    Public Order myOrder; Public Customer myCustomer; Public Invoice myInvoice;

    Such variables can then be used to store actual object instances and subsequently to serve as recipients of messages sent by other objects. In the previous code fragment, the variable myOrder is an instance of Order. After the myOrder object is created, a message can be sent to it and myOrder will respond, provided that the operation is supported by myOrder's interface.

    Java and Message Passing

    Central to any object-oriented language is the ability to pass messages between objects. In later chapters you will see that work is done in a system only by objects that collaborate (by sending messages) to accomplish a goal (which is specified in a use-case) of the system.

    Java doesn't allow stray functions floating around that are not attached to a class. In fact, Java demands this. Unfortunately, as my previous story suggested, just saying that a language requires everything to be packaged in classes doesn't mean that the class design will be robust, let alone correct.

    Java supports message passing, which is central to the use of Java's object-oriented features. The format closely resembles the syntax of other languages, such as C++ and Visual Basic. In the following code fragment, assume that a variable called myCustomer, of type Customer, is defined and that an operation called calcTotalValue() is defined for Customer. Then the calcTotalValue() message being sent to the myCustomer object in Java would look like this:

    myCustomer.calcTotalValue();

    Many developers feel that, in any other structured language, this is just a fancy way of calling a procedure. Calling a procedure and sending a message are similar in that, once invoked, both a procedure and a message implement a set of well-defined steps. However, a message differs in two ways:

  • There is a designated receiver, the object. Procedures have no designated receiver.

  • The interpretation of the message—that is, the how-to code (called the method) used to respond to the message—can vary with different receivers. This point will become more important later in the chapter, when polymorphism is reviewed.

  • The concepts presented in this book rely heavily on classes and the messaging that takes place between their instances, or objects.

    Java and Encapsulation

    Recall that a class exposes itself to the outside world via its public interface and that this should be done through exposure to operations only, and not attributes. Java supports encapsulation via its ability to declare both attributes and operations as public, private, or protected. In UML this is called visibility.

    Using the code from the previous Order example, suppose you want to set the value of the orderDate attribute. In this case, you should do so with an operation. An operation that gets or sets values is usually called a getter or a setter, respectively, and collectively such operations are called accessors. The local copy of the order date, orderDate, is declared private. (Actually, all attributes of a class should be declared private or protected, so that they are accessible only via operations exposed as public to the outside world.)

    Encapsulation provides some powerful capabilities. To the outside world, the design can hide how it derives its attribute values. If the orderTotal attribute is stored in the Order object, the corresponding get operation defined previously looks like this:

    public long getOrderTotal() { return orderTotal; }

    This snippet of code would be invoked if the following code were executed by an interested client:

    private long localTotal; private Order localOrder; localOrder = New Order(); localTotal = localOrder.getOrderTotal()

    However, suppose the attribute orderTotal isn't kept as a local value of the Order class, but rather is derived via another mechanism (perhaps messaging to its OrderLine objects). If Order contains OrderLine objects (declared as a Vector or ArrayList of OrderLine objects called myOrderLines) and OrderLine knows how to obtain its line totals via the message getOrderLineTotal(), then the corresponding get operation for orderTotal within Order will look like this:

    public long getOrderTotal() { long totalAmount=0; for (int i=0; i < myOrderLines.length; i++) { totalAmount = totalAmount + myOrderLines[i].getOrderLineTotal(); } return totalAmount; }

    This code cycles through the myOrderLines collection, which contains all the Orderline objects related to the Order object, sending the getOrderLineTotal() message to each of Order's OrderLine objects. The getOrderTotal() operation will be invoked if the following code is executed by an interested client:

    long localTotal; Order myOrder; myOrder = new Order(); localTotal = localOrder.getOrderTotal()

    Notice that the "client" code didn't change. To the outside world, the class still has an orderTotal attribute. However, you have hidden, or encapsulated, just how the value was obtained. This encapsulation allows the class's interface to remain the same (hey, I have an orderTotal that you can ask me about), while the class retains the flexibility to change its implementation in the future (sorry, how we do business has changed and now we must derive orderTotal like this). This kind of resiliency is one of the compelling business reasons to use an object-oriented programming language in general.

    Java and Inheritance

    The inclusion of inheritance is often the most cited reason for granting a language object-oriented status. There are two kinds of inheritance: interface and implementation. As we shall see, Java is one of the few languages that makes a clear distinction between the two.

    Interface inheritance (Figure 2-2) declares that a class that is inheriting an interface will be responsible for implementing all of the method code of each operation defined in that interface. Only the signatures of the interface are inherited; there is no method or how-to code.

    FIGURE 2-2 Interface inheritance

    Implementation inheritance (Figure 2-3) declares that a class that is inheriting an interface may, at its option, use the method code implementation already established for the interface. Alternatively, it may choose to implement its own version of the interface. In addition, the class inheriting the interface may extend that interface by adding its own operations and attributes.

    FIGURE 2-3 Implementation inheritance

    Each type of inheritance should be scrutinized and used in the appropriate setting. Interface inheritance is best used under the following conditions:

  • The base class presents a generic facility, such as a table lookup, or a derivation of system-specific information, such as operating-system semantics or unique algorithms.

  • The number of operations is small.

  • The base class has few, if any, attributes.

  • Classes realizing or implementing the interface are diverse, with little or no common code.

  • Implementation inheritance is best used under the following conditions:

  • The class in question is a domain class that is of primary interest to the application (i.e., not a utility or controller class).

  • The implementation is complex, with a large number of operations.

  • Many attributes and operations are common across specialized implementations of the base class.

  • Some practitioners contend that implementation inheritance leads to a symptom called the fragile base class problem. Chiefly, this term refers to the fact that over time, what were once common code and attributes in the superclass may not stay common as the business evolves. The result is that many, if not all, of the subclasses, override the behavior of the superclass. Worse yet, the subclasses may find themselves overriding the superclass, doing their own work, and then invoking the same operation again on the superclass. These practitioners espouse the idea of using only interface inheritance. Particularly with the advent of Java and its raising of the interface to a first-class type, the concept and usage of interface-based programming have gained tremendous momentum.

    As this book evolves, keeping in mind the pointers mentioned here when deciding between the two types of inheritance will be helpful. Examples of both constructs will be presented in the theme project that extends throughout this book.

    Implementation Inheritance

    Java supports implementation inheritance with the extends keyword. A class wanting to take advantage of implementation inheritance simply adds an extendsClassName statement to its class definition. To continue the previous example, suppose you have two different types of orders, both warranting their own subclasses: Commercial and Retail. You would still have an Order class (which isn't instantiated directly and which is called abstract). The previous fragment showed the code for the Order class. Following is the code for the Commercial class.

    package com.jacksonreed; public class Commercial extends Order { public Commercial() { } /* Unique Commercial code goes here */ }

    Implementation inheritance allows the Commercial class to utilize all attributes and operations defined in Order. This will be done automatically by the Java Virtual Machine (JVM) in conjunction with the language environment. In addition, implementation inheritance has the ability to override and/or extend any of Order's behavior. Commercial may also add completely new behavior if it so chooses.

    Interface Inheritance

    Java supports interface inheritance with the implements keyword. A class wanting to realize a given interface (actually being responsible for the method code) simply adds an implements InterfaceName statement. However, unlike extension of one class by another class, implementation of an interface by a class requires that the interface be specifically defined as an interface beforehand.

    Looking again at the previous example with Order, let's assume that this system will contain many classes—some built in this release, and some built in future releases—that need the ability to price themselves. Remember from earlier in this chapter that one of the indicators of using interface inheritance is the situation in which there is little or no common code but the functional intent of the classes is the same. This pricing functionality includes three services: the abilities to calculate tax, to calculate an extended price, and to calculate a total price. Let's call the operations for these services calcExtendedPrice(), calcTax(), and calcTotalPrice(), respectively, and assign them to a Java interface called IPrice. Sometimes interface names are prefixed with the letter I to distinguish them from other classes:

    package com.jacksonreed; interface IPrice { long calcExtendedPrice(); long calcTax(); long calcTotalPrice(); }

    Notice that the interface contains only operation signatures; it has no implementation code. It is up to other classes to implement the actual behavior of the operations. For the Order class to implement, or realize, the IPrice interface, it must include the implements keyword followed by the interface name:

    public class Order implements IPrice { }

    If you try to implement an interface without providing implementations for all of its operations, your class will not compile. Even if you don't want to implement any method code for some of the operations, you still must have the operations defined in your class.

    One very powerful aspect of interface inheritance is that a class can implement many interfaces at the same time. For example, Order could implement the IPrice interface and perhaps a search interface called ISearch. However, a Java class may extend from only one other class.

    Java and Polymorphism

    Polymorphism is one of those $50 words that dazzles the uninformed and sounds really impressive. In fact, polymorphism is one of the most powerful features of any object-oriented language.

    Roget's II: The New Thesaurus cross-references the term polymorphism to the main entry of variety. That will do for starters. Variety is the key to polymorphism. The Latin root for polymorphism means simply "many forms." Polymorphism applies to operations in the object-oriented context. So by combining these two thoughts, you could say that operations are polymorphic if they are identical (not just in name but also in signatures) but offer variety in their implementations.

    Polymorphism is the ability of two different classes each to have an operation that has the same signature, while having two very different forms of method code for the operation. Note that to take advantage of polymorphism, either an interface inheritance or an implementation inheritance relationship must be involved.

    In languages such as COBOL and FORTRAN, defining a routine to have the same name as another routine will cause a compile error. In object-oriented languages such as Java and C++, several classes might have an operation with the same signature. Such duplication is in fact encouraged because of the power and flexibility it brings to the design.

    As mentioned previously, the implements and extends keywords let the application take advantage of polymorphism. As we shall see, the sample project presented later in this book is an order system for a company called Remulak Productions. Remulak sells musical equipment, as well as other types of products. There will be a Product class, as well as Guitar, SheetMusic, and Supplies classes.

    Suppose, then, that differences exist in the fundamental algorithms used to determine the best time to reorder each type of product (called the economic order quantity, or EOQ). I don't want to let too much out of the bag at this point, but there will be an implementation inheritance relationship created with Product as the ancestor class (or superclass) and the other three classes as its descendants (or subclasses). The scenario that follows uses implementation inheritance with a polymorphic example. Note that interface inheritance would yield the same benefits and be implemented in the same fashion.

    To facilitate extensibility and be able to add new products in the future in a sort of plug-and-play fashion, we can make calcEOQ() polymorphic. To do this in Java, Product would define calcEOQ() as abstract, thereby informing any inheriting subclass that it must provide the implementation. A key concept behind polymorphism is this: A class implementing an interface or inheriting from an ancestor class can be treated as an instance of that ancestor class. In the case of a Java interface, the interface itself is a valid type.

    For example, assume that a collection of Product objects is defined as a property of the Inventory class. Inventory will support an operation, getAverageEOQ(), that needs to calculate the average economic order quantity for all products the company sells. To do this requires that we iterate over the collection of Product objects called myProducts to get each object's unique economic order quantity individually, with the goal of getting an average:

    public long getAverageEOQ() { long totalAmount=0; for (int i=0; i < myProducts.length; i++) { totalAmount = totalAmount + myProducts[i].calcEOQ(); } return totalAmount / myProducts.length; }

    But wait! First of all, how can Inventory have a collection of Product objects when the Product class is abstract (no instances were ever created on their own)? Remember the maxim from earlier: Any class implementing an interface or extending from an ancestor class can be treated as an instance of that interface or extended class. A Guitar "is a" Product, SheetMusic "is a" Product, and Supplies "is a" Product. So anywhere you reference Guitar, SheetMusic, or Supplies, you can substitute Product.

    Resident in the array myProducts within the Inventory class are individual concrete Guitar, SheetMusic, and Supplies objects. Java figures out dynamically which object should get its own unique calcEOQ() message. The beauty of this construct is that later, if you add a new type of Product—say, Organ—it will be totally transparent to the Inventory class. That class will still have a collection of Product types, but it will have four different ones instead of three, each of which will have its own unique implementation of the calcEOQ() operation.

    This is polymorphism at its best. At runtime, the class related to the object in question will be identified and the correct "variety" of the operation will be invoked. Polymorphism provides powerful extensibility features to the application by letting future unknown classes implement a predictable and well-conceived interface without affecting how other classes deal with that interface.



    Direct Download of over 5500 Certification Exams

    3COM [8 Certification Exam(s) ]
    AccessData [1 Certification Exam(s) ]
    ACFE [1 Certification Exam(s) ]
    ACI [3 Certification Exam(s) ]
    Acme-Packet [1 Certification Exam(s) ]
    ACSM [4 Certification Exam(s) ]
    ACT [1 Certification Exam(s) ]
    Admission-Tests [13 Certification Exam(s) ]
    ADOBE [93 Certification Exam(s) ]
    AFP [1 Certification Exam(s) ]
    AICPA [2 Certification Exam(s) ]
    AIIM [1 Certification Exam(s) ]
    Alcatel-Lucent [13 Certification Exam(s) ]
    Alfresco [1 Certification Exam(s) ]
    Altiris [3 Certification Exam(s) ]
    Amazon [2 Certification Exam(s) ]
    American-College [2 Certification Exam(s) ]
    Android [4 Certification Exam(s) ]
    APA [1 Certification Exam(s) ]
    APC [2 Certification Exam(s) ]
    APICS [2 Certification Exam(s) ]
    Apple [69 Certification Exam(s) ]
    AppSense [1 Certification Exam(s) ]
    APTUSC [1 Certification Exam(s) ]
    Arizona-Education [1 Certification Exam(s) ]
    ARM [1 Certification Exam(s) ]
    Aruba [6 Certification Exam(s) ]
    ASIS [2 Certification Exam(s) ]
    ASQ [3 Certification Exam(s) ]
    ASTQB [8 Certification Exam(s) ]
    Autodesk [2 Certification Exam(s) ]
    Avaya [96 Certification Exam(s) ]
    AXELOS [1 Certification Exam(s) ]
    Axis [1 Certification Exam(s) ]
    Banking [1 Certification Exam(s) ]
    BEA [5 Certification Exam(s) ]
    BICSI [2 Certification Exam(s) ]
    BlackBerry [17 Certification Exam(s) ]
    BlueCoat [2 Certification Exam(s) ]
    Brocade [4 Certification Exam(s) ]
    Business-Objects [11 Certification Exam(s) ]
    Business-Tests [4 Certification Exam(s) ]
    CA-Technologies [21 Certification Exam(s) ]
    Certification-Board [10 Certification Exam(s) ]
    Certiport [3 Certification Exam(s) ]
    CheckPoint [41 Certification Exam(s) ]
    CIDQ [1 Certification Exam(s) ]
    CIPS [4 Certification Exam(s) ]
    Cisco [318 Certification Exam(s) ]
    Citrix [48 Certification Exam(s) ]
    CIW [18 Certification Exam(s) ]
    Cloudera [10 Certification Exam(s) ]
    Cognos [19 Certification Exam(s) ]
    College-Board [2 Certification Exam(s) ]
    CompTIA [76 Certification Exam(s) ]
    ComputerAssociates [6 Certification Exam(s) ]
    Consultant [2 Certification Exam(s) ]
    Counselor [4 Certification Exam(s) ]
    CPP-Institue [2 Certification Exam(s) ]
    CPP-Institute [1 Certification Exam(s) ]
    CSP [1 Certification Exam(s) ]
    CWNA [1 Certification Exam(s) ]
    CWNP [13 Certification Exam(s) ]
    Dassault [2 Certification Exam(s) ]
    DELL [9 Certification Exam(s) ]
    DMI [1 Certification Exam(s) ]
    DRI [1 Certification Exam(s) ]
    ECCouncil [21 Certification Exam(s) ]
    ECDL [1 Certification Exam(s) ]
    EMC [129 Certification Exam(s) ]
    Enterasys [13 Certification Exam(s) ]
    Ericsson [5 Certification Exam(s) ]
    ESPA [1 Certification Exam(s) ]
    Esri [2 Certification Exam(s) ]
    ExamExpress [15 Certification Exam(s) ]
    Exin [40 Certification Exam(s) ]
    ExtremeNetworks [3 Certification Exam(s) ]
    F5-Networks [20 Certification Exam(s) ]
    FCTC [2 Certification Exam(s) ]
    Filemaker [9 Certification Exam(s) ]
    Financial [36 Certification Exam(s) ]
    Food [4 Certification Exam(s) ]
    Fortinet [13 Certification Exam(s) ]
    Foundry [6 Certification Exam(s) ]
    FSMTB [1 Certification Exam(s) ]
    Fujitsu [2 Certification Exam(s) ]
    GAQM [9 Certification Exam(s) ]
    Genesys [4 Certification Exam(s) ]
    GIAC [15 Certification Exam(s) ]
    Google [4 Certification Exam(s) ]
    GuidanceSoftware [2 Certification Exam(s) ]
    H3C [1 Certification Exam(s) ]
    HDI [9 Certification Exam(s) ]
    Healthcare [3 Certification Exam(s) ]
    HIPAA [2 Certification Exam(s) ]
    Hitachi [30 Certification Exam(s) ]
    Hortonworks [4 Certification Exam(s) ]
    Hospitality [2 Certification Exam(s) ]
    HP [750 Certification Exam(s) ]
    HR [4 Certification Exam(s) ]
    HRCI [1 Certification Exam(s) ]
    Huawei [21 Certification Exam(s) ]
    Hyperion [10 Certification Exam(s) ]
    IAAP [1 Certification Exam(s) ]
    IAHCSMM [1 Certification Exam(s) ]
    IBM [1532 Certification Exam(s) ]
    IBQH [1 Certification Exam(s) ]
    ICAI [1 Certification Exam(s) ]
    ICDL [6 Certification Exam(s) ]
    IEEE [1 Certification Exam(s) ]
    IELTS [1 Certification Exam(s) ]
    IFPUG [1 Certification Exam(s) ]
    IIA [3 Certification Exam(s) ]
    IIBA [2 Certification Exam(s) ]
    IISFA [1 Certification Exam(s) ]
    Intel [2 Certification Exam(s) ]
    IQN [1 Certification Exam(s) ]
    IRS [1 Certification Exam(s) ]
    ISA [1 Certification Exam(s) ]
    ISACA [4 Certification Exam(s) ]
    ISC2 [6 Certification Exam(s) ]
    ISEB [24 Certification Exam(s) ]
    Isilon [4 Certification Exam(s) ]
    ISM [6 Certification Exam(s) ]
    iSQI [7 Certification Exam(s) ]
    ITEC [1 Certification Exam(s) ]
    Juniper [64 Certification Exam(s) ]
    LEED [1 Certification Exam(s) ]
    Legato [5 Certification Exam(s) ]
    Liferay [1 Certification Exam(s) ]
    Logical-Operations [1 Certification Exam(s) ]
    Lotus [66 Certification Exam(s) ]
    LPI [24 Certification Exam(s) ]
    LSI [3 Certification Exam(s) ]
    Magento [3 Certification Exam(s) ]
    Maintenance [2 Certification Exam(s) ]
    McAfee [8 Certification Exam(s) ]
    McData [3 Certification Exam(s) ]
    Medical [69 Certification Exam(s) ]
    Microsoft [374 Certification Exam(s) ]
    Mile2 [3 Certification Exam(s) ]
    Military [1 Certification Exam(s) ]
    Misc [1 Certification Exam(s) ]
    Motorola [7 Certification Exam(s) ]
    mySQL [4 Certification Exam(s) ]
    NBSTSA [1 Certification Exam(s) ]
    NCEES [2 Certification Exam(s) ]
    NCIDQ [1 Certification Exam(s) ]
    NCLEX [2 Certification Exam(s) ]
    Network-General [12 Certification Exam(s) ]
    NetworkAppliance [39 Certification Exam(s) ]
    NI [1 Certification Exam(s) ]
    NIELIT [1 Certification Exam(s) ]
    Nokia [6 Certification Exam(s) ]
    Nortel [130 Certification Exam(s) ]
    Novell [37 Certification Exam(s) ]
    OMG [10 Certification Exam(s) ]
    Oracle [279 Certification Exam(s) ]
    P&C [2 Certification Exam(s) ]
    Palo-Alto [4 Certification Exam(s) ]
    PARCC [1 Certification Exam(s) ]
    PayPal [1 Certification Exam(s) ]
    Pegasystems [12 Certification Exam(s) ]
    PEOPLECERT [4 Certification Exam(s) ]
    PMI [15 Certification Exam(s) ]
    Polycom [2 Certification Exam(s) ]
    PostgreSQL-CE [1 Certification Exam(s) ]
    Prince2 [6 Certification Exam(s) ]
    PRMIA [1 Certification Exam(s) ]
    PsychCorp [1 Certification Exam(s) ]
    PTCB [2 Certification Exam(s) ]
    QAI [1 Certification Exam(s) ]
    QlikView [1 Certification Exam(s) ]
    Quality-Assurance [7 Certification Exam(s) ]
    RACC [1 Certification Exam(s) ]
    Real-Estate [1 Certification Exam(s) ]
    RedHat [8 Certification Exam(s) ]
    RES [5 Certification Exam(s) ]
    Riverbed [8 Certification Exam(s) ]
    RSA [15 Certification Exam(s) ]
    Sair [8 Certification Exam(s) ]
    Salesforce [5 Certification Exam(s) ]
    SANS [1 Certification Exam(s) ]
    SAP [98 Certification Exam(s) ]
    SASInstitute [15 Certification Exam(s) ]
    SAT [1 Certification Exam(s) ]
    SCO [10 Certification Exam(s) ]
    SCP [6 Certification Exam(s) ]
    SDI [3 Certification Exam(s) ]
    See-Beyond [1 Certification Exam(s) ]
    Siemens [1 Certification Exam(s) ]
    Snia [7 Certification Exam(s) ]
    SOA [15 Certification Exam(s) ]
    Social-Work-Board [4 Certification Exam(s) ]
    SpringSource [1 Certification Exam(s) ]
    SUN [63 Certification Exam(s) ]
    SUSE [1 Certification Exam(s) ]
    Sybase [17 Certification Exam(s) ]
    Symantec [134 Certification Exam(s) ]
    Teacher-Certification [4 Certification Exam(s) ]
    The-Open-Group [8 Certification Exam(s) ]
    TIA [3 Certification Exam(s) ]
    Tibco [18 Certification Exam(s) ]
    Trainers [3 Certification Exam(s) ]
    Trend [1 Certification Exam(s) ]
    TruSecure [1 Certification Exam(s) ]
    USMLE [1 Certification Exam(s) ]
    VCE [6 Certification Exam(s) ]
    Veeam [2 Certification Exam(s) ]
    Veritas [33 Certification Exam(s) ]
    Vmware [58 Certification Exam(s) ]
    Wonderlic [2 Certification Exam(s) ]
    Worldatwork [2 Certification Exam(s) ]
    XML-Master [3 Certification Exam(s) ]
    Zend [6 Certification Exam(s) ]





    References :


    Dropmark : http://killexams.dropmark.com/367904/11675412
    Wordpress : http://wp.me/p7SJ6L-14F
    Issu : https://issuu.com/trutrainers/docs/000-634
    Dropmark-Text : http://killexams.dropmark.com/367904/12155518
    Blogspot : http://killexamsbraindump.blogspot.com/2017/11/free-pass4sure-000-634-question-bank_15.html
    RSS Feed : http://feeds.feedburner.com/WhereCanIGetHelpToPass000-634Exam
    Box.net : https://app.box.com/s/1qprrxdvstyb3rildp77p0yo5esm9a5y
    publitas.com : https://view.publitas.com/trutrainers-inc/000-634
    zoho.com : https://docs.zoho.com/file/5r1nh6574f65ec73c4bbea02b82a3d17570da
    Calameo : http://en.calameo.com/books/004923526de9afc52e316






    View Complete PDF »

    We Make Sure Q&A work for you!

    See Entry Test Preparation   |   Project Management, English Tests Home

    Pass4sure PDFs (Pass4sure Questions and Answers), Viewable at all devices like PC Windows (all versions), Linux (All versions), Mac / iOS (iPhone/iPad and all other devices), Android (All versions). It support High Quality Printable book format. You can print and carry anywhere with you, as you like.

    Testing and Training Engine Software (Pass4sure Exam Simulator) Compatible with All Windows PC (Windows 10/9/8/7/Vista/XP/2000/98 etc). Mac (Through Wine, Virtual Windows PC, Dual boot). It prepares your test for all the topics of exam, gives you exam tips and tricks by asking tricky questions, uses latest practice quiz to train you for the real test taking experience in learning mode as well as real test mode. Provides performance graphs and training history etc.

    View Complete Article »

    More Useful Links about 000-634

    Certification Vendors Here   |   View Exams, Latest Home

    Information Links



    References:


    000-634 brain dump | 000-634 bootcamp | 000-634 real questions | 000-634 practical test | 000-634 practice questions | 000-634 test prep | 000-634 study material | 000-634 exam prep | 000-634 study guide | 000-634 online exam | 000-634 training material | 000-634 mock test | 000-634 mock exam | 000-634 free practice tests | 000-634 free test | 000-634 test answers | 000-634 online test | 000-634 test questions | 000-634 exam questions | 000-634 exam papers | 000-634 assessment test sample | 000-634 reading practice test | 000-634 practice test | 000-634 test questions | 000-634 exam prep | 000-634 online exam | 000-634 free prep | 000-634 exam answers | 000-634 sample test questions | 000-634 test exam | 000-634 exam results | 000-634 free exam papers | 000-634 exam dumps | 000-634 past bar exams | 000-634 exam preparation | 000-634 free online test | 000-634 practice exam | 000-634 test questions and answers | 000-634 exam test | 000-634 test sample | 000-634 sample test | 000-634 test practice | 000-634 free test online | 000-634 question test | 000-634 model question | 000-634 exam tips | 000-634 certification sample | 000-634 pass exam | 000-634 prep questions | 000-634 entrance exam | 000-634 essay questions | 000-634 sample questions | 000-634 study questions | 000-634 mock questions | 000-634 test example | 000-634 past exams | 000-634 quest bars

    Download Free PDF »

    Services Overview

    We provide Pass4sure Questions and Answers and exam simulators for the candidates to prepare their exam and pass at first attempt.

    Contact Us

    As a team are working hard to provide the candidates best study material with proper guideline to face the real exam.

    Address: 15th floor, 7# building 16 Xi Si Huan.
    Telephone: +86 10 88227272
    FAX: +86 10 68179899
    Others: +301 - 0125 - 01258
    E-mail: info@Killexams.com



       

       

     

     



    .
     

      .