1. vrije Universiteit amsterdamPostacademische Cursus Informatie Technologie Object-Oriented Software Engineering Anton Eliëns Vrije Universiteit, Amsterdam 27 april 1999 http://www.cs.vu.nl/~eliens/cmg/html/oo http://www.cs.vu.nl/~eliens/online/courses/cmg/oo

2. vrije Universiteit amsterdamPostacademische Cursus Informatie Technologie Topics: Basic OO technology Application Framework(s) Universal Modeling Language Design Patterns Project Management Current developments and trends

3. vrije Universiteit amsterdamPostacademische Cursus Informatie Technologie Introduction If OO is the Answer, What is the Question?

4. vrije Universiteit amsterdamPostacademische Cursus Informatie Technologie Keywords and phrases the OO lifecycle -- modelling encapsulation, inheritance, delegation, polymorphism specification and implementation inheritance design by contract interfaces, components and frameworks idioms, patterns, software architecture

5. vrije Universiteit amsterdamPostacademische Cursus Informatie Technologie Basic OO Technolology Technology determines the effectiveness of the approach

6. vrije Universiteit amsterdamPostacademische Cursus Informatie Technologie Concepts Encapsulation Data hiding Inheritance Polymorphism

7. vrije Universiteit amsterdamPostacademische Cursus Informatie Technologie Encapsulation An object contains data and methods It provides a boundary: to the world outside to its ‘children’

8. vrije Universiteit amsterdamPostacademische Cursus Informatie Technologie Information hiding Reduces complexity Allows you to defer implementations Remember: Ignorance is bliss Helps in decoupling components

9. vrije Universiteit amsterdamPostacademische Cursus Informatie Technologie Inheritance A mechanism for code-sharing Supports incremental development Organize by classification Allows for abstract interfaces

10. vrije Universiteit amsterdamPostacademische Cursus Informatie Technologie Polymorphism An object may have multiple types An abstract type: when it is used A concrete type: when it is created An object’s type is determined by its behavior An object’s type is determined by the messages it allows

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12. vrije Universiteit amsterdamPostacademische Cursus Informatie Technologie Design by Contract formal basis -- pre and post conditions refinement -- by inheritance or polymorphism runtime checks -- division of responsibility see Ch. 3, Contracts

13. vrije Universiteit amsterdamPostacademische Cursus Informatie Technologie The San Francisco Framework How useful is an OO framework?

14. vrije Universiteit amsterdamPostacademische Cursus Informatie Technologie Example - San Francisco Framework

15. vrije Universiteit amsterdamPostacademische Cursus Informatie Technologie A framework is... a collection of components a generic solution for a class of problems a frame of mind for solving problems a set of architectural constraints

16. vrije Universiteit amsterdamPostacademische Cursus Informatie Technologie The San Francisco Framework is meant to develop business applications is based on Java technology may solve 70% of your problem leaves 30% (minimum) to solve for you may set a standard or may fail to do so...

17. vrije Universiteit amsterdamPostacademische Cursus Informatie Technologie San Francisco - motivation The project was started when several software vendors asked IBM to help modernizing their application products However, there were several barriers preventing them from being able to update their applications

18. vrije Universiteit amsterdamPostacademische Cursus Informatie Technologie Barriers to modernizing (1) The problem of how to retrain their development staff to effectively use OO technology. (2) The risk involved in moving to a new technology. (3) moving -> the cost of the change The software developers realized they needed some basic infrastructure. Many companies could not develop this infrastructure themselves.

19. vrije Universiteit amsterdamPostacademische Cursus Informatie Technologie San Francisco - the press The San Francisco project helps to solve these problems by offering developers Business Process Components, designed as frameworks that provides an object oriented infrastructure, a consistent application programming model, and some default business logic The frameworks make it easier to move to OO technology because developers use well-tested services instead of building their own.

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21. vrije Universiteit amsterdamPostacademische Cursus Informatie Technologie San Francisco Framework - layers Core Business Process Layer - the highest Common Business Objects Layer - middle Foundation Layer - lowest

22. vrije Universiteit amsterdamPostacademische Cursus Informatie Technologie Core Business Processes The objective for this layer is to create a sound architecture and highly extensible OO implementation for the basic structure and behavior which any application provider delivering a solution in the application doamin would require: Accounts Receivable/Payable Ledger General Ledger Framework Sales Order Management Framework Purchase Order Management

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24. vrije Universiteit amsterdamPostacademische Cursus Informatie Technologie Common Business Objects Business Objects common to multiple domains Common Application level Services CBO: Business Partner Address Number - decimal structure Currency - how many euros in a dollar?

25. vrije Universiteit amsterdamPostacademische Cursus Informatie Technologie Foundation Layer Foundation Object Model Classes Utilities in other words: it provides the infrastructure comment: reinventing the wheel is not a big problem, because the wheel is a terrific invention

26. vrije Universiteit amsterdamPostacademische Cursus Informatie Technologie Foundation Object Model Classes Command Entity Dependent Collection/Iterator Factory you need to study Design Patterns to appreciate these...

27. vrije Universiteit amsterdamPostacademische Cursus Informatie Technologie Using the San Francisco Framework … The San Francisco Frameworks are designed to make many types of extensions easy for application dvelopers: overriding the default business logic in supplied methods adding additional attributes to existing classes adding additional methods to existing classes from the report: Complete documentation will be provided …

28. vrije Universiteit amsterdamPostacademische Cursus Informatie Technologie Example Two classes: Receipt and Purchase order Line default attributes, methods default business logic: inspect Quality on receipt Extension: enhance this logic subclass Receipt override inspection method change logic to include checks against supplier tables, and hazardous or high value products

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30. vrije Universiteit amsterdamPostacademische Cursus Informatie Technologie San Francisco - issues Standards: OMG/CORBA Business Issues Technology Integration: Compound Documents: Lotus Notes, JavaBeans, Active X Business process Modelling and Control: workflow engines may be used as glue … Internet/Intranet and Java: applications may be designed …. Conclusions: … a bit premature...

31. vrije Universiteit amsterdamPostacademische Cursus Informatie Technologie Universal Modeling Language … why you need models? Models are necessary to communicate, to stabilize abstractions as a reference for the implementation and maintenance and you need an agreement on the notation and formalisms in which you express your models

32. vrije Universiteit amsterdamPostacademische Cursus Informatie Technologie Unified Modeling Language class diagrams -- conceptual structure use cases -- functional requirements interaction diagrams -- operational aspects package and deployment -- implementation state and activity -- dynamic behavior See http://www.rational.com/uml and UML Distilled, [Fowler97].

33. vrije Universiteit amsterdamPostacademische Cursus Informatie Technologie UML - Quick Reference and Overview adapted from the Rational Rose Quick Reference at http://www.rational.com/uml/qr and Principles of O-O Software Development Appendix UML

34. vrije Universiteit amsterdamPostacademische Cursus Informatie Technologie Class diagrams Describe properties of classes and their (inter) relations

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36. vrije Universiteit amsterdamPostacademische Cursus Informatie Technologie Interaction diagram To gain an operational intuition to check calling chains

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38. vrije Universiteit amsterdamPostacademische Cursus Informatie Technologie Use cases Define the boundary between the system and its uses Might be a good subject for a paper...

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40. vrije Universiteit amsterdamPostacademische Cursus Informatie Technologie Collaboration diagrams To further analyze the relations between classes augments: class diagram and interaction diagram

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42. vrije Universiteit amsterdamPostacademische Cursus Informatie Technologie Visibility properties More implementation oriented But remember: ignorance is bliss...

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44. vrije Universiteit amsterdamPostacademische Cursus Informatie Technologie Component and Deployment diagram Primarily for the system architect

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46. vrije Universiteit amsterdamPostacademische Cursus Informatie Technologie Associations, roles, aggregations You may augment the model to any extent Personally, I believe in constraints See for example: Fowler - Analysis Patterns

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49. vrije Universiteit amsterdamPostacademische Cursus Informatie Technologie Dynamic object behavior - state transitions State transition diagrams are rarely used except in applications that require scheduling: workflow, simulation, concurrency

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52. vrije Universiteit amsterdamPostacademische Cursus Informatie Technologie Examples - interactive drawing tool - the reactor pattern (events) - business process modeling - the observer pattern

53. vrije Universiteit amsterdamPostacademische Cursus Informatie Technologie Interactive drawing tool

54. vrije Universiteit amsterdamPostacademische Cursus Informatie Technologie Reactor (event-handling) pattern

55. vrije Universiteit amsterdamPostacademische Cursus Informatie Technologie Reactor - Interaction diagram (events)

56. vrije Universiteit amsterdamPostacademische Cursus Informatie Technologie Business process modeling

57. vrije Universiteit amsterdamPostacademische Cursus Informatie Technologie (simulation) event state transition diagram

58. vrije Universiteit amsterdamPostacademische Cursus Informatie Technologie Observer Pattern

59. vrije Universiteit amsterdamPostacademische Cursus Informatie Technologie A Catalogue of Design patterns a common design vocabulary documentation and learning aid an adjunct to existing methods a target for redesign see the GOF Design Patterns and the Patterns Homepage

60. vrije Universiteit amsterdamPostacademische Cursus Informatie Technologie The Pattern Schema: structure Name - handle –increases design vocabulary Problem - when to apply –explains the problem and the conflict Solution - general arrangement –design, responsibilities, collaborations Consequences - trade-off's –to understand the costs and benefit

61. vrije Universiteit amsterdamPostacademische Cursus Informatie Technologie Causes for Redesign (1) 1. creating an object by specifying a class explicitly -- Abstract Factory, Factory Method, Prototype 2. dependence on specific operations -- Chain of Responsibility, Command 3. dependence on hardware & software platforms -- Abstract Factory, Bridge 4. dependence on object implementation or representation -- Abstract Factory, Bridge, Memento, Proxy

62. vrije Universiteit amsterdamPostacademische Cursus Informatie Technologie Causes for Redesign (2) 5. algorithm dependence -- Builder, Iterator, Strategy, Template Method, Visitor 6. extending functionality by subclassing -- Bridge, Chain, Composite, Decorator, Observer 7. tight coupling -- Abstract Factory, Bridge, Chain of Responsibilities, Command, Facade, Mediator, Observer 8. inability to alter classes conveniently -- Adaptor, Decorator, Visitor

63. vrije Universiteit amsterdamPostacademische Cursus Informatie Technologie Kinds of Patterns creational patterns -- Factory, Singleton,... structural patterns -- Adaptor, Composite, Bridge,... behavioral patterns -- Mediator, Observer, Command, … see UML

64. vrije Universiteit amsterdamPostacademische Cursus Informatie Technologie Managing O-O Projects Did YOU ever manage a project?

65. vrije Universiteit amsterdamPostacademische Cursus Informatie Technologie Critical Success Factors use incremental scheduling and staging find and fix failing ideas develop a habit of delivering get: sponsor, project manager, technical leader

66. vrije Universiteit amsterdamPostacademische Cursus Informatie Technologie Key Failure Indicators absence of incremental development use of C++ in commercial IS see Surviving Object-Oriented Projects: A Managers Guide

67. vrije Universiteit amsterdamPostacademische Cursus Informatie Technologie OO - Success and Failure OO = technology + mind-set it might be new technology to your organisation developers love it! requires and enables communication between groups adopting OO may succeed or fail!

68. vrije Universiteit amsterdamPostacademische Cursus Informatie Technologie Possible benefits - responsiveness responsiveness - variations on a theme responsiveness to change! time-to-market communication - developers, users, executives maintenance, reuse, productivity GUI development morale -- cutting-edge technology

69. vrije Universiteit amsterdamPostacademische Cursus Informatie Technologie Drawbacks Are YOU underestimating? productivity takes time hazards of C++ (and Java,...) reuse is difficult establishing a software process business-modelling or software design? CASE helps? You will pay for: training, experience, tools, consultants,...

70. vrije Universiteit amsterdamPostacademische Cursus Informatie Technologie The hazards of C++? C++ won the language war over Eiffel, Objective-C, SOM, C@+, and Java? Java -- relative simplicity and portability

71. vrije Universiteit amsterdamPostacademische Cursus Informatie Technologie Managing (the complexity of) C++ misconception: C++ is like C consider using another language Why does C++ exist? - engineering and systems programming create a subset of the language design and coding standards use people with knowledge!

72. vrije Universiteit amsterdamPostacademische Cursus Informatie Technologie Risk-reduction Strategies look carefully all around the project detect the risks! list the risks in order work on the risks in order of danger see Risk Avoidance Patterns

73. vrije Universiteit amsterdamPostacademische Cursus Informatie Technologie Technology and Trends UML Risks Java Frameworks Contracts CORBA Patterns DOT

74. vrije Universiteit amsterdamPostacademische Cursus Informatie Technologie Frameworks Frameworks = Components + Patterns Ralph Johnson, CACM Nov. 1997 The benefits of frameworks stem from the inversion of control. A Framework defines an Architecture?

75. vrije Universiteit amsterdamPostacademische Cursus Informatie Technologie Software Architecture Software Architecture = a set of rules, guidelines, interfaces, and conventions used to define how components and applications communicate and interoperate with each other... see patterns

76. vrije Universiteit amsterdamPostacademische Cursus Informatie Technologie CORBA the issue is standardisation by means of interfaces looking for consensus this differs from a de-facto standard imposed by market share... see Ch 11: Application integration -- standards see frameworks

77. vrije Universiteit amsterdamPostacademische Cursus Informatie Technologie Java - perspectives Internet applications Software Engineering Language Design System Development Computer Science IT (in) Business Global Village Informatie, januari 99: Java - een kwestie van vraag en aanbod

78. vrije Universiteit amsterdamPostacademische Cursus Informatie Technologie Dimensions of Risks Knowledge Teaming Productivity Ownership Distractions Don't discuss risks, unless you know how to do Project Management

79. vrije Universiteit amsterdamPostacademische Cursus Informatie Technologie Conclusions OO offers –a valid metaphor for SE –powerful technology –maturing design methods and notations –a rich set of patterns

80. vrije Universiteit amsterdamPostacademische Cursus Informatie Technologie Yet beware of the learning curve simplified hype cutting edge technology (over) ambitious projects

81. vrije Universiteit amsterdamPostacademische Cursus Informatie Technologie Assignments: Write a paper about one of the following topics. The paper may discuss concepts or focus on a case study. –The Unified Modelling Language -- UML –Frameworks -- for example San Francisco Write a comparative study of object-oriented analysis and design methods, focussing on aspects of project management. Describe a case study concerning the deployment of design patterns.

82. vrije Universiteit amsterdamPostacademische Cursus Informatie Technologie Course material Chapter 1 Additional material –Ch 3: Design by Contract –Ch 11: Methods and Tools –Object Tutorials Resources –http://www.rational.com -- Rational Rose, UML –http://www.ibm.com/java/sanfrancisco -- IBM Java San Francisco Framework Papers and Reports –http://www.rational.com/uml/html/summary -- UML Summary –http://www.ibm.com/Java/Sanfrancisco/prd_summary.html -- San Francisco Technical Summary