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000-833 protest Oriented Analysis and Design - fraction 1 (Analysis)

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000-833 exam Dumps Source : Object Oriented Analysis and Design - fraction 1 (Analysis)

Test Code : 000-833
Test title : Object Oriented Analysis and Design - fraction 1 (Analysis)
Vendor title : IBM
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IBM protest Oriented Analysis and

Object-Oriented analysis and Design | existent Questions and Pass4sure dumps

This chapter is from the publication 

analysis emphasizes an investigation of the issue and requirements, in locality of a solution. as an example, if a brand modern on-line trading device is desired, how will it's used? What are its functions?

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

Design emphasizes a conceptual solution (in application and hardware) that fulfills the necessities, in preference to its implementation. as an example, a description of a database schema and utility objects. Design concepts regularly exclude low-level or "obvious" details—obvious to the meant consumers. eventually, designs will moreover be carried out, and the implementation (similar to code) expresses the genuine and comprehensive realized design.

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

positive evaluation and design were summarized in the phrase enact the revise constituent (evaluation), and enact the constituent revise (design).

Object-Oriented evaluation And Design — Introduction (part 1) | existent Questions and Pass4sure dumps

The thought Of Object-Orientation

Object-orientation is what’s known as a programming paradigm. It’s not a language itself but a set of concepts it really is supported by means of many languages.

in case you aren’t criterion with the ideas of object-orientation, you may additionally retract a sight on the narrative of Object-Oriented Programming.

If every Little thing they enact in these languages is object-oriented, it ability, we're oriented or focused around objects.

Now in an object-oriented language, this one gigantic program will as an alternative be prick up apart into self contained objects, nearly enjoy having a yoke of mini-courses, each protest representing a special a fraction of the utility.

and each protest incorporates its own information and its own estimable judgment, and that they talk between themselves.

These objects aren’t random. They symbolize the manner you talk and feel about the hardship you are trying to remedy to your actual existence.

They characterize things enjoy personnel, photographs, pecuniary institution money owed, spaceships, asteroids, video segment, audio data, or something exists to your software.

Object-Oriented analysis And Design (OOAD)

It’s a structured formula for examining, designing a system by using applying the item-oriented ideas, and boost a group of graphical gadget models total through the structure lifestyles cycle of the application.

OOAD in the SDLC

The software lifestyles cycle is usually divided up into tiers going from abstract descriptions of the problem to designs then to code and trying out and finally to deployment.

The earliest stages of this process are analysis (requirements) and design.

The dissimilarity between evaluation and design is commonly described as “what Vs how”.

In analysis developers travail with users and locality experts to contour what the system is meant to do. Implementation details are presupposed to be normally or absolutely disregarded at this phase.

The goal of the analysis fraction is to create a model of the system inspite of constraints reminiscent of preempt know-how. here's usually executed by means of exercise circumstances and abstract definition of essentially the most crucial objects the exercise of conceptual model.

The design fraction refines the evaluation model and applies the obligatory know-how and different implementation constrains.

It specializes in describing the objects, their attributes, habits, and interactions. The design model should acquire the entire details required in order that programmers can invoke the design in code.

They’re optimal performed in an iterative and incremental utility methodologies. So, the activities of OOAD and the developed models aren’t executed once, they are able to revisit and refine these steps constantly.

Object-Oriented evaluation

within the object-oriented analysis, we …

  • Elicit necessities: define what does the utility should do, and what’s the hardship the software making an attempt to transparent up.
  • Specify requirements: relate the requirements, usually, using exercise circumstances (and scenarios) or user experiences.
  • Conceptual mannequin: establish the faultfinding objects, refine them, and define their relationships and deportment and draw them in an light diagram.
  • We’re not going to cover the first two actions, just the final one. These are already explained in constituent in necessities Engineering.

    Object-Oriented Design

    The analysis side identifies the objects, their relationship, and deportment the usage of the conceptual model (an abstract definition for the objects).

    while in design part, they relate these objects (with the aid of creating class diagram from conceptual diagram — always mapping conceptual mannequin to category diagram), their attributes, behavior, and interactions.

    in addition to applying the software design principles and patterns which could be lined in later tutorials.

    The enter for object-oriented design is equipped through the output of object-oriented evaluation. however, analysis and design may chance in parallel, and the consequences of 1 activity will moreover be used by using the different.

    within the object-oriented design, we …

  • Describe the classes and their relationships the usage of classification diagram.
  • Describe the interplay between the objects the exercise of sequence diagram.
  • observe application design ideas and design patterns.
  • a category diagram offers a visual illustration of the classes you want. And here is the locality you glean to be definitely inescapable about object-oriented principles enjoy inheritance and polymorphism.

    Describing the interactions between these objects allows you to improved bethink the responsibilities of the diverse objects, the behaviors they deserve to have.

    — different diagrams

    there are many different diagrams they will exercise to model the system from distinctive perspectives; interactions between objects, constitution of the system, or the deportment of the gadget and the course it responds to hobbies.

    It’s total the time about choosing the prerogative diagram for the prerogative want. accomplish certain to understand which diagrams could be advantageous when considering or discussing a condition that isn’t clear.

    equipment modeling and the discrete models they are able to exercise will be discussed subsequent.

    system Modeling

    gadget modeling is the procedure of developing models of the equipment, with every mannequin representing a different views of that equipment.

    probably the most essential point about a system mannequin is that it leaves out aspect; It’s an abstract representation of the system.

    The models are usually in accordance with graphical notation, which is almost always according to the notations within the Unified Modeling Language (UML). different models of the gadget enjoy mathematical model; a detailed system description.

    models are used total over the analysis process to champion to elicit the necessities, prerogative through the design manner to explicate the gadget to engineers, and after implementation to doc the device constitution and operation.

    different views

    We may multiply a model to signify the gadget from different views.

  • exterior, the locality you model the context or the atmosphere of the system.
  • interaction, where you mannequin the interplay between components of a device, or between a system and other programs.
  • Structural, where you model the organization of the system, or the structure of the data being processed by the system.
  • Behavioral, where you model the dynamic habits of the gadget and how it respond to routine.
  • Unified Modeling Language (UML)

    The unified modeling language become the tolerable modeling language for object-oriented modeling. It has many diagrams, besides the fact that children, essentially the most diagrams which are conventional are:

  • Use case diagram: It suggests the interplay between a gear and it’s ambiance (clients or techniques) within a particular condition.
  • classification diagram: It suggests the diverse objects, their relationship, their behaviors, and attributes.
  • Sequence diagram: It indicates the interactions between the distinctive objects within the system, and between actors and the objects in a device.
  • State computing device diagram: It indicates how the system respond to exterior and inner events.
  • recreation diagram: It indicates the ride of the statistics between the methods within the gadget.
  • that you could enact diagramming travail on paper or on a whiteboard, at the least within the initial degrees of a task. however there are some diagramming tools as a course to champion you to attract these UML diagrams.

    record: IBM Outpaces opponents in utility construction application marketplace for Seventh Straight year | existent Questions and Pass4sure dumps

    source: IBM

    June 13, 2008 08:00 ET

    ARMONK, ny--(Marketwire - June 13, 2008) - IBM (NYSE: IBM) nowadays introduced that analyst firm Gartner, Inc.* and market analysis enterprise Evans statistics Corp. acquire ranked IBM as the chief within the application structure application market. These rankings arrive just as IBM is projecting greater than 12,000 people will attend its 2008 IBM Rational application evolution Conferences in 13 international locations worldwide.

    Gartner named IBM the global market share leader in application evolution in accordance with complete utility salary in 2007 and Evans information Corp. survey respondents who were users of IBM Rational utility Developer ranked it the number 1 integrated Developer ambiance (IDE) for user satisfaction. this is the seventh consecutive 12 months that Gartner has ranked IBM the chief and 2nd consecutive 12 months that IBM Rational application Developer changed into chosen as the Developer's option preempt IDE by course of the 1,200 builders international taking fraction in the survey.

    in line with the independent Gartner record, IBM is the main market share vendor in total software earnings, with 37.eight percent market share -- superior market share than its three closest opponents combined. The worldwide application structure application market grew greater than 10% percent in 2007 to very nearly $6.9 billion, in accordance with Gartner.

    IBM became moreover mentioned for its typical leadership in accordance with total utility salary for 2007 across software construction market sub-categories, together with SCCM disbursed, protest Oriented analysis & Design and Java Platform ad tool. Telelogic, currently bought by course of IBM, had a 2007 marketshare of forty.6 % within the requirements Elicitation and management category in line with complete software earnings.

    "With the upward thrust of globally dispensed software evolution teams, consumers are searching for skilled providers to profit them collaborate in an open and transparent manner," mentioned Dr. Daniel Sabbah, common supervisor, IBM Rational software. "We conform with the powerful response from the Evans information and Gartner experiences coincides with the remarks we've got bought from consumers about IBM's approach round advantageous application birth."

    IBM Kicks off the world's Most Attended Developer convention sequence

    This marketshare information coincides with IBM's announcement that over 12,000 members are anticipated to attend the 15 IBM Rational application construction Conferences deliberate around the globe. Following the event held final week in Orlando, FL, IBM will retract the array on the highway to 17 cities including Sharm El Sheikh, Egypt; San Paulo, Brazil; Bangalore, India; Shanghai, China; Rome and Milan, Italy.

    For convention attendees using an iPhone, IBM is releasing a conference scheduler written in commercial enterprise technology Language (EGL) to enable iPhone clients to dynamically journey the IBM Rational utility structure conference via an interface that they feel at ease with. using internet 2.0 and convivial engineering ideas, users can deliver remarks on and chat about sessions, navigate the convention looking for tracks and movements, and exercise artistic expertise that suggests which talks the person should attend next in keeping with preferences.

    on the annual IBM Rational application structure convention in Orlando, Florida, greater than 3,500 attendees realized about modern software and courses that aid valued clientele seriously change how they're birth application on a global scale. The announcement of recent products, services and company associate initiatives are designed to transform how IBM Rational utility can assist customers compel superior price and performance from their globally allotted application investments.

    shoppers unable to attend the conference in the community can view the keynote presentations on IBM tv.

    IBM helps developers abide aggressive in trendy quick-paced evolution ambiance. imaginative classes similar to IBM developerWorks, the premier technical useful resource for application developers, and IBM alphaWorks, IBM's rising applied sciences outlet, give an online group for the builders of today and day after today. developers who're unbiased utility vendors can retract competencies of income and marketing equipment, ability-building lessons and technical aid with the aid of becoming a member of the international IBM PartnerWorld software. IBM's tutorial Initiative and IBM Rational application structure convention are examples of the continuing researching and neighborhood-constructing courses needed by students, educators and developers international.

    For greater suggestions, consult with

    *"Market Share: utility structure software, international, 2007" by course of Laurie Wurster, Teresa Jones and Asheesh Raina, may additionally 2008.

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    Object Oriented Analysis and Design - fraction 1 (Analysis)

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    Object-Oriented Analysis And Design — Introduction (Part 1) | existent questions and Pass4sure dumps

    The Concept Of Object-Orientation

    Object-orientation is what’s referred to as a programming paradigm. It’s not a language itself but a set of concepts that is supported by many languages.

    If you aren’t chummy with the concepts of object-orientation, you may retract a sight at The narrative of Object-Oriented Programming.

    If everything they enact in these languages is object-oriented, it means, they are oriented or focused around objects.

    Now in an object-oriented language, this one large program will instead be split apart into self contained objects, almost enjoy having several mini-programs, each protest representing a different fraction of the application.

    And each protest contains its own data and its own logic, and they communicate between themselves.

    These objects aren’t random. They portray the course you talk and reflect about the problem you are trying to solve in your existent life.

    They portray things enjoy employees, images, bank accounts, spaceships, asteroids, video segment, audio files, or whatever exists in your program.

    Object-Oriented Analysis And Design (OOAD)

    It’s a structured fashion for analyzing, designing a system by applying the object-orientated concepts, and develop a set of graphical system models during the evolution life cycle of the software.

    OOAD In The SDLC

    The software life cycle is typically divided up into stages going from abstract descriptions of the problem to designs then to code and testing and finally to deployment.

    The earliest stages of this process are analysis (requirements) and design.

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

    In analysis developers travail with users and domain experts to define what the system is supposititious to do. Implementation details are supposititious to be mostly or totally ignored at this phase.

    The goal of the analysis side is to create a model of the system regardless of constraints such as preempt technology. This is typically done via exercise cases and abstract definition of the most Important objects using conceptual model.

    The design side refines the analysis model and applies the needed technology and other implementation constrains.

    It focuses on describing the objects, their attributes, behavior, and interactions. The design model should acquire total the details required so that programmers can implement the design in code.

    They’re best conducted in an iterative and incremental software methodologies. So, the activities of OOAD and the developed models aren’t done once, they will revisit and refine these steps continually.

    Object-Oriented Analysis

    In the object-oriented analysis, we …

  • Elicit requirements: Define what does the software exigency to do, and what’s the problem the software trying to solve.
  • Specify requirements: relate the requirements, usually, using exercise cases (and scenarios) or user stories.
  • Conceptual model: Identify the Important objects, refine them, and define their relationships and deportment and draw them in a simple diagram.
  • We’re not going to cover the first two activities, just the final one. These are already explained in detail in Requirements Engineering.

    Object-Oriented Design

    The analysis side identifies the objects, their relationship, and deportment using the conceptual model (an abstract definition for the objects).

    While in design phase, they relate these objects (by creating class diagram from conceptual diagram — usually mapping conceptual model to class diagram), their attributes, behavior, and interactions.

    In addition to applying the software design principles and patterns which will be covered in later tutorials.

    The input for object-oriented design is provided by the output of object-oriented analysis. But, analysis and design may occur in parallel, and the results of one activity can be used by the other.

    In the object-oriented design, we …

  • Describe the classes and their relationships using class diagram.
  • Describe the interaction between the objects using sequence diagram.
  • Apply software design principles and design patterns.
  • A class diagram gives a visual representation of the classes you need. And here is where you glean to be really specific about object-oriented principles enjoy inheritance and polymorphism.

    Describing the interactions between those objects lets you better understand the responsibilities of the different objects, the behaviors they exigency to have.

    — Other diagrams

    There are many other diagrams they can exercise to model the system from different perspectives; interactions between objects, structure of the system, or the deportment of the system and how it responds to events.

    It’s always about selecting the prerogative diagram for the prerogative need. You should realize which diagrams will be useful when thinking about or discussing a situation that isn’t clear.

    System modeling and the different models they can exercise will be discussed next.

    System Modeling

    System modeling is the process of developing models of the system, with each model representing a different perspectives of that system.

    The most Important aspect about a system model is that it leaves out detail; It’s an abstract representation of the system.

    The models are usually based on graphical notation, which is almost always based on the notations in the Unified Modeling Language (UML). Other models of the system enjoy mathematical model; a detailed system description.

    Models are used during the analysis process to profit to elicit the requirements, during the design process to relate the system to engineers, and after implementation to document the system structure and operation.

    Different Perspectives

    We may develop a model to portray the system from different perspectives.

  • External, where you model the context or the environment of the system.
  • Interaction, where you model the interaction between components of a system, or between a system and other systems.
  • Structural, where you model the organization of the system, or the structure of the data being processed by the system.
  • Behavioral, where you model the dynamic deportment of the system and how it respond to events.
  • Unified Modeling Language (UML)

    The unified modeling language become the criterion modeling language for object-oriented modeling. It has many diagrams, however, the most diagrams that are commonly used are:

  • Use case diagram: It shows the interaction between a system and it’s environment (users or systems) within a particular situation.
  • Class diagram: It shows the different objects, their relationship, their behaviors, and attributes.
  • Sequence diagram: It shows the interactions between the different objects in the system, and between actors and the objects in a system.
  • State machine diagram: It shows how the system respond to external and internal events.
  • Activity diagram: It shows the rush of the data between the processes in the system.
  • You can enact diagramming travail on paper or on a whiteboard, at least in the initial stages of a project. But there are some diagramming tools that will profit you to draw these UML diagrams.

    MET CS 770 Object-Oriented Analysis & Design | existent questions and Pass4sure dumps

    Last updated: November 13, 2002 Recent updates are often in red.

    Contacting Eric Braude changed if this is red Materials changed if this is red Forums changed if this is red Overview changed if this is red Grading changed if this is red Project Organization changed if this is red Homework and Due Dates changed if this is red        Phase 3 Required Background changed if this is red Learning Objectives changed if this is red Syllabus and Dates for Classes changed if this is red Overview

    A major engineering problem today is the predictable evolution of amenable software-intensive systems. The object-oriented paradigm is an Important fraction of such development.

    Object-oriented methods can be divided into languages, distribution, and analysis and design. There change in the language category, particularly Java and C#. Distribution includes the exercise of vendor libraries of classes and moreover distributed objects as specified by the protest Management Group etc.  Basic to the entire enterprise, however, are analysis and design, which has remained remarkable stable for years. Object-Oriented Analysis and Design includes the overall goals of the protest paradigm, the selection of classes, the relationships among them, and their utilization to implement systems.

    Required Background

    A information of C++ or Java (MET CS 565) and software engineering methods (MET CS 673) are required.   It is preferable to acquire taken Design Patterns (MET CS 665).

    Materials and references

    The recommended textbook is “Applying UML and Patterns: An Introduction to Object-Oriented Analysis and Design, and the Unified Process ” by Larman (Prentice Hall) 2nd edition, Published July 2001, 627 pages, ISBN 0130925691.  This is the first time that this instructor has used this book, and it is not transparent how much the reserve will be used.

    The instructor will provide notes for total classes.

    Other references:

  • The Unified Modeling Language User lead by Booch et al (Prentice Hall) ISBN0-201-57168-4
  • The Unified Modeling Language Reference Manual James Rumbaugh, Ivar Jacobson, Grady Booch Addison-Wesley Pub Co; ISBN: 020130998X
  • Design Patterns by Gamma et al
  • Object-Oriented Software Engineering by I Jacobson
  • Object-Oriented Analysis & Design by G. Booch
  • Modeling the world in data by S. Schlaer and S. Mellor
  • Modeling the world in states by S. Schlaer and S. Mellor
  • The Unified fashion draft
  • Object-oriented Analysis by P. Coad and E. Yourdon
  • Object-oriented Design by P. Coad and E. Yourdon
  • Object-oriented Programming by P. Coad and A Nicola
  • Software Engineering: An Object-Oriented Perspective by Eric Braude
  • Learning Objectives

    Students will be able to …

  • … analyze problems from an protest perspective
  • … create OO designs which are ready for coding
  • … implement a pilot OO project
  • Grading

    The course will consist of homework and a project, weighted as follows:

    1.      Homework:                  30%

    2.      Project:                        70%

    There are three phases for the project, graded as follows:

  • phase 1 (problem statement):                            1/9
  • phase 2 (analysis):                                             2/9
  • phase 3 (design):                                               1/3
  • phase 4 (implementation and faultfinding review): 1/3
  • Parts are evaluated equally unless otherwise stated.

    Late homework is not accepted unless there is a intuition why it was impossible for you. If there is such an impossibility, the travail will be graded on a pass/fail basis.

    Project Organization

    You will be required to submit an analyzed, designed and implemented project according to the deadlines shown in the schedule. detailed requirements will follow.

    With the instructor’s permission, it may be workable to substitute total or fraction of the project with an investigation of tools for OOA&D such as Rational Rose or Together.  This will require a detailed evaluation and an investigation of how these tools are being used extensively in a particular company.

    Teams two are permitted, and will be evaluated at a higher standard. total members must know total parts.

    You will be required to give a presentation on at least two of the phases in your project.


    This syllabus is matter to about 15% modification.

    The order of topics will be driven by the notes, which the instructor will hand out, not by the textbook. The textbook will serve as background and reference.

    Wk. Date Topic Text



    Times are approximate.  survey “date homework due” section for final dates

    1 9/3
  • Review Syllabus
  • Review Software evolution Process
  • Notes 0-1 Phase 1 assigned 2 9/10
  • Introduction, Overview, and Goals of Design
  • UML as required
  • Extreme programming and refactoring
  • Notes 1-3 3 9/17
  • Requirements I: exercise Cases
  • Notes 13 fraction 1 Presentations;

    Assign side 2

    4 9/24
  • Requirements II: Sequence Diagrams
  • Notes 13 fraction 2 Phase 1 due; 5 10/1
  • Requirements III:  Completing Domain Classes
  • Writing detailed Requirements
  • Review Student Designs
  • Notes 13 fraction 3

    Larman 10

    6 10/8 Notes 14 fraction 1 Assign side 3 7 10/22 To be determined Presentations; side 2 due; 8 10/29
  • Review Design Patterns as required
  • Discussion of Tools
  • Review Student Designs
  • Notes 4-6 9 11/5
  • Frameworks
  • Review Student Designs
  • Presentations on architectures 10 11/12
  • Design Topics
  • Review Student Designs
  • Notes 14 fraction 2 Assign side 4

    Phase 3 due

    11 11/19 Presentations on detailed designs 12 11/26
  • Detailed Design
  • Review Student Designs
  • Presentations 13 12/3
  • Implementing OO designs
  • Shlaer-Mellor
  • Presentation of results (1 of 2) 14 12/10
  • Presentations on Finished Applications
  • Phase 4 due Presentation of results (2 of 2)
  • Notes are from Software Design (Braude, to be published by Wiley in March 2002)
  • ** Applying UML and Patterns: … (Larman)
  • Dates Homework is due

    Num-ber Name Due date Project side 1 9/24 1 “Design Issues” 9/17 1 3.4 (Pass Fail) 9/17 Project side 2: (10/2/2002


    1.Attach first a copy of your side 1.  Respond specifically to whatever comments I may acquire made on your side 1.   You can write these directly on the copy.


    Show the sequence diagrams for at least the two exercise cases you acquire introduced.  Key them to the exercise case steps, which you should number.3.List requirements by “domain class” paragraphs, including

    — The testable functionality that the application will definitely accomplish

    –What you would enjoy to acquire the application accomplish if time permits

    Criterion: a. Requirements clearly written. (A = very transparent description of application’s goals; no detail omitted)

    4.Provide a class diagram for your project consisting of total of the domain classes as well as the domain packages that you will use.


    b. Clarity and completeness Sufficiency of key classes for committed requirements and exercise cases (A = very transparent class meanings; no domain class missing no other domain classes required)

    g. Economy (A = no redundancy at total in the class model)

    Here are some typical improvements.

    Most leeway for improvement

    1.      accomplish your domain names specific to your application; e.g., PetStoreTransaction, FootballGame, FootballTeam rather than Transaction or Game or Team.

    2.      exercise the “entities” section correctly.  This applies when there are specific entities that the application is required to have. It does not involve entities that will be created at runtime that you can’t specify entirely at requirements time.

    3.      Many internal classes acquire corresponding GUI classes.  For example, PetStoreAccount entities may glean their data from a PetStoreAccountGUI entity.  Specify the latter in its own category rather than under PetStoreAccount.

    4.      In your requirements, distinguish between the initiator and the purport of functionality.

    For example, under “Courses” a functionality might be “12.1.5 The application shall be able to array the catalog description of each course in the following format …”  (Corresponds to class Course).  Under the “Course GUI” paragraph an event might be “When the array course button is pressed, the functionality described in section 12.1.5 is initated.”  Under the “Student GUI” paragraph an event might be “When the expose course button is pressed, the functionality described in section 12.1.5 is initated.” Etc.

    Do not shriek “12.1.5 When the array course button is pressed on the Course GUI, the application can array the catalog description of each course in the following format …”  Otherwise you will acquire a maintenance nightmare and a poor mapping to the design and implementation.


    Room for improvement

    1. Most







    objects are not sensitive to events unless they are GUI objects.  Buttons are examples.  Many objects acquire functionality that may be invoked as a result of an event on an

    other object.  For example, a customer’s information may be displayed when the button is clicked.  But “display” is a office of Customer: Any one of clients can invoke it, some event-sensitive and others not.  The protest with (direct) event reaction is the button, not the customer.

    2. In your requirements document, don’t shriek “The customer shall involve a title …” (which is extreme English).  Instead: “The application shall maintain the title of customers ….”

    3. Distinguish between objects and protest aggregates.  For example, you could acquire a “Customers” requirements paragraph with functionality such as “App shall be able to send a customer profile to the central database.”  This will correspond to a class Customer.  You could moreover acquire a “Customer List”  paragraph with functionality such as “It shall be workable to add modern customers …”  This will correspond to a class such as CustomerList.

    4. Don’t dissipate words. In particular, give a sentence or two under each paragraph that adds value.


    1.4 Customers

    This section describes the requirements for customers.


    1.4 Customers

    The application shall track the customers of the video store as follows. …


    10/22 3 Clown problem 10/9/02

    Draw a class model for an application for drawing human figures.  The picture shown is a typical product of the application.  The figures are always neck-upward; mouths are always lines, necks always rectangles, etc. – the shapes that emerge in the figure.  Assume that the traffic will never change — but they want to be able to easily upgrade the shop’s capability within these constraints (e.g., draw necks with various colors, modern kinds of brim lines).  The class model should accomplish pattern drawing convenient (e.g., allowing the retrieval of previously constructed pattern parts). expose attributes or operations whenever they clarify your solution.  involve useful abstractions (but to extend the current business).

    There is no requirement to retract into account the GUI for the application (icons, menu’s etc.)

    Here is a scenario:

    The user … pulls onto the monitor “abeLincolnFace14” (which excludes the ears and neck)

    … adds “ear123” on the left by dragging to its vicinity and releasing

    The application places ear123 in a revise position

    The user invokes the “complete with suitable parts” command.

    The application

    … completes the pattern with a neck and hat that it considers most suitable.

    … creates an ear on the right, complete with matching position, interior texture and color, and styles of brim lines

    Criteria: a. completeness relative to requirements (A = adequate classes for requirements, including preempt generalizations)

    b. economy of classes (A = no more than necessary for requirements)

    10/29 4 14.1 – 14.6 11/5 see more below see below

    Project side 3: Due 11/12

    1.  Attach a copy of your side 2 as graded by me, with specific responses to whatever comments I may acquire made on your side 2.

    2. Provide a class diagram for your project, showing inheritance and aggregation.  expose key methods, key dependencies, and inheritance and aggregation.   exercise your packages and Facades to avoid a single overwhelming figure.

    3. expose at least one additional model that completes your design.


    a. Clarity of the model (A = very transparent class meanings; very transparent organization; no unnecessary details)

    b. Adequacy of class model for effecting the requirements.  (A= detailed enough to clearly allow an implementation that satisfies the requirements.)

    g. Completeness **** of models to specify the entire design. (A=right models selected; clearly no gaps in description)

    Most leeway for improvement

    1. If you exercise a data rush diagram, indicate the data types that flow.

    2. If you exercise a data rush diagram, indicate the functionality at each processing node.

    3. In the interest of clarity, expose the relationships among the packages.  You can employ <<uses>> relationships.  Omit the classes from such a figure.

    Room for improvement

    1. In this course they did not give signification to solid lines with arrows.  explicate what you signify by them, or don’t exercise them.

    2. be specific about associations: enact you signify two-way aggregations?

    3. You acquire introduced a class whose title does not indicate a transparent purpose and which is not a domain class.  explicate it’s purpose.

    A Little leeway for improvement

    1. …..

    Project side 4:     Due 12/10

    Section 1 Attach Phases 2 and 3. Response to my comments on side 3. ( not graded, but required)

    Section 2 expose representative input and output.

    Section 3 explicate the application of total of the steps covered in the notes — explicate if they did not apply.

    (criterion: a. Clarity and completeness — A = total relevant steps thoroughly implemented where applicable and explained where not)

    Section 4 Provide a complete class diagram and other preempt model(s), structure on the models you submitted for side 3.

    (criterion: b. clarity and completeness — A = very clearly chosen and arranged models)

    Section 5 Account of the degree to which you accomplished your requirements as given in side 2.  delight refer to them by number (e.g., 11.3.5).

    (criterion: g. degree of accomplishment.  A = excellent functional capabilities for a graduate course)

    Section 6. Source code.

    (d. criterion: clarity — A = extremely transparent layout & code; each fraction easily traceable to the corresponding design element)

    Please …

    note that your class diagrams and code must be consistent;

    indicate total differences with prior design decisions;

    indicate total sections using numbered tabs (e.g., Post-it notes)

    Forums — past and present

    Fall 2001

    Fall 2002 email to the group is:

    Object-oriented design patterns in the kernel, fraction 2 | existent questions and Pass4sure dumps

    Please consider subscribing to LWN

    Subscriptions are the lifeblood of If you appreciate this content and would enjoy to survey more of it, your subscription will profit to ensure that LWN continues to thrive. delight visit this page to join up and maintain LWN on the net.

    June 7, 2011

    This article was contributed by Neil Brown

    In the first fraction of this analysis they looked at how the polymorphic side of object-oriented programming was implemented in the Linux kernel using regular C constructs. In particular they examined fashion dispatch, looked at the different forms that vtables could take, and the circumstances where sever vtables were eschewed in preference for storing office pointers directly in objects. In this conclusion they 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 enjoy subtype inheritance, where a concrete or "final" ilk inherits some data fields from a "virtual" parent type. They will call this "data inheritance" to emphasize the fact that it is the data rather than the deportment 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 create in the Linux kernel, and total 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 moreover the least flexible, is to declare a union as one constituent 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 void 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 when ext3 was added.

    This approach to data inheritance is simple and straightforward, but is moreover fairly clumsy. There are two obvious problems. Firstly, every modern filesystem implementation needs to add an extra territory to the union "u". With 3 fields this may not appear enjoy 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 very 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 they will survey shortly. The second is a existent problem and the general ugliness of the design encouraged change. Early in the 2.5 evolution train 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 moreover 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 preempt memory to store its own structure without any exigency 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 hardship 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 locality 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 ilk safety and makes it harder to organize fields in the inode to glean optimal performance - as some kernel developers are wont to do.

    The solution was to exercise the list_entry() macro to accomplish 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 exercise this pattern of data structure embedding. The list_entry() macro did exactly what was needed and so it was used despite the extreme name. This practice lasted until 2.5.28 when a modern container_of() macro was added which implemented the very functionality as list_entry(), though with slightly more ilk 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 hardship was that the filesystem had to be amenable for allocating the inode - it could no longer be allocated by common code as the common code did not acquire enough information to preempt the revise 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 eminent earlier, the union pattern was not an impenetrable barrier to adding modern filesystems independently. This is because the union u had one more territory that was not an "inode_info" structure. A generic pointer territory 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 preempt a sever 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 modern 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 moreover required writing more error-handling code. moreover 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 exigency 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 exercise of the generic_ip pointer. It was certainly used, but not by the major, high-performance filesystems.

    Though this pattern has problems it is soundless in wide use. struct super_block has an s_fs_info pointer which serves the very 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 course to store filesystem-private data in a super_block. A simple search in the Linux involve 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 ilk 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 efficacious vehicle to insert these three patterns they enact not array the replete scope of any of them so it is useful to sight further afield and survey what else they can learn.

    A survey of the exercise 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 sweep of different modules (different filesystems) each wanted to extend an inode in different ways. In most places where unions are used there are a minuscule fixed number of subtypes of the ground ilk and there is Little expectation of more being added. A simple instance 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 dissimilarity encoded in a union. As NFSv4 uses the very 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 ilk has a different ilk 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 transparent whether these examples should be considered as the very pattern as the original struct inode. enact they really portray different subtypes of a ground type, or is it just one ilk with internal variants? The Eiffel object-oriented programming language does not champion variant types at total except through subtype inheritance so there is clearly a school of thought that would want to handle total usages of union as a form of subtyping. Many other languages, such as C++, provide both inheritance and unions allowing the programmer to accomplish a choice. So the respond is not clear.

    For their purposes it doesn't really matter what they call it as long as they know where to exercise each pattern. The examples in the kernel fairly clearly expose that when total of the variants are understood by a single module, then a union is a very preempt 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 sever pieces of code, then one of the other mechanisms is preferred. The exercise of unions for this case has almost completely disappeared with only struct cycx_device remaining as an instance of a deprecated pattern.

    Problems with void pointers

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

    Examining total the different uses that void pointers can be do to would be well beyond the scope of this article. Instead they will restrict their attention to just one modern usage which relates to data inheritance and illustrates how the untamed nature of void pointers makes it hard to recognize their exercise in data inheritance. The instance they will exercise to explicate this usage is struct seq_file used by the seq_file library which makes it light to synthesize simple text files enjoy some of those in /proc. The "seq" fraction 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 modern seq_file it allocates a struct seq_file and assigns it to the private_data territory of the struct file which is being opened. This is a straightforward instance of void pointer based data inheritance where the struct file is the ground ilk 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 territory which is a void pointer and it can be used by clients of seq_file to add extra state to the file. For instance 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 territory 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 territory itself. This certainly seems enjoy a sensible optimization - performing an allocation to store a single pointer would be a dissipate - but it highlights exactly the source of confusion that was suggested earlier: that when you sight at a void pointer you don't really know what is it pointing at, or why.

    To accomplish it a bit clearer what is happening here, it is helpful to imagine "void *private" as being enjoy a union of every different workable 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 they survey 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 soundless has not just one but two void pointers, both with names suggesting that they are for private exercise 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 shroud 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 exigency 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 exercise this field, one appears to supervene that intention while the other two exercise 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 transparent 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 transparent is that an apparently "private" void pointer can be intended for various qualitatively different uses and, as they acquire 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 they leave unions and void pointers behind a sight at struct page may be interesting. This structure uses both of these patterns, though they are hidden fairly due to historical baggage. This instance 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 do 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 respond kmalloc() requests. Others are simply fraction of a multi-page allocation or maybe are on a free list waiting to be used. Each of these different exercise cases could be seen as a subtype of the general class of "page", and in most cases exigency 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 very struct page describing it, so if the efficacious ilk of the page is to change - as it must as the demands for different uses of memory change over time - the ilk of the struct page must change within the lifetime of that structure. While many ilk systems are designed assuming that the ilk of an protest is immutable, they find here that the kernel has a very existent exigency for ilk mutability. Both unions and void pointers allow types to change and as noted, struct page uses both.

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

    When the primary subtype in exercise 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 territory 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 very size and this is one of them. Most users of this territory actually store a pointer here and acquire to cast it back and forth. The "buffer_head" library provides macros attach_page_buffers and page_buffers to set and glean this field.

    So while struct page is not the most elegant example, it is an informative instance 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 workable subtypes is not known in advance, it seems to be increasingly the preferred choice. To gain a replete understanding of it they will again exigency 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 animated 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 exercise is the data inheritance embedding that they acquire already discussed. The third is enjoy it but importantly different. This third exercise is typified by struct list_head and other structs used as an embedded anchor when creating abstract data types.

    The exercise of an embedded anchor enjoy 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 protest can acquire several struct list_heads embedded - struct inode has six (if they involve the similar hlist_node). So it is probably best to reflect of this sort of embedding more enjoy 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 being 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 protest with an independent being will acquire a reference counter, sometimes a simple atomic_t or even an int, though often a more specific struct kref. When an protest is created using several levels of inheritance the reference counter could be buried quite deeply. For instance a struct usb_device embeds a struct device which embeds struct kobject which has a struct kref. So usb_device (which might in circle be embedded in a structure for some specific device) does acquire 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 acquire no reference counter, acquire no independent being and simply provide a service to other data structures.

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

    It moreover means that, when designing a data structure, it is Important to reflect about lifetime issues and whether this data structure should acquire its own reference counter or whether it should depend on something else for its lifetime management. That is, whether it is an protest in its own right, or simply a service provided to other objects. These issues are not really modern and apply equally to void pointer inheritance. However an Important dissimilarity with void pointers is that it is relatively light to change your reason 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 prerogative determination 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 modern 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() office is called which can optionally preempt and initialize any extension object. By contrast when structure embedding is used the structure needs to be allocated by the lowest smooth device driver which then initializes its own fields and calls in to common code to initialize the common fields.

    Continuing the struct inode instance from above which has an alloc_inode() fashion in the super_block to request allocation, they find that initialization is provided for with inode_init_once() and inode_init_always() champion functions. The first of these is used when the previous exercise of a piece of memory is unknown, the second is adequate by itself when they know that the memory was previously used for some other inode. They survey this very pattern of an initializer office sever 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.


    In exploring the exercise of fashion dispatch (last week) and data inheritance (this week) in the Linux kernel they find that while some patterns appear to dominate they are by no means universal. While almost total data inheritance could be implemented using structure embedding, unions provide existent value in a few specific cases. Similarly while simple vtables are common, mixin vtables are very Important and the talent to delegate methods to a related protest can be valuable.

    We moreover find that there are patterns in exercise with Little to recommend them. Using void pointers for inheritance may acquire an initial simplicity, but causes longer term wastage, can intuition confusion, and could nearly always be replaced by embedded inheritance. Using NULL pointers to indicate default deportment is similarly a poor election - 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 moreover a useful document to study. Such study can find elegant practical solutions to existent problems, and some less elegant solutions. The willing student can pursue the former to profit better their mind, and pursue the latter to profit better the kernel itself. With that in mind, the following exercises might be of interest to some.

  • As inodes now exercise 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 eminent in the text, struct seq_file can be extended both through "void pointer" and a limited form of "union" data inheritance. explicate how seq_open_private() allows this structure to moreover be extended through "embedded structure" data inheritance and give an instance 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 protest to contain fields that not total 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 exercise of the proposed open() fashion for inodes might profit here.

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

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