1. vrije Universiteit amsterdamPostacademische Cursus Informatie Technologie Object-Oriented Software Engineering Anton Eliëns Vrije Universiteit, Amsterdam 28 october 1998 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: OO technology The OO life cycle Project Management Application Frameworks 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 Characterisations of OO 1. encapsulation + inheritance 2. data abstraction + polymorphism 3. interfaces + components 4. types + implementations 5. CORBA + Application Frameworks 6. Java + nothing else 7. a metaphor + hype 8. everything I can sell … Let's have a look at the Introduction from Principles of Object-Oriented Software Development

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

7. 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

8. 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

9. 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!

10. 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

11. 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,...

12. 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

13. 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!

14. 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

15. vrije Universiteit amsterdamPostacademische Cursus Informatie Technologie Case studies: Application Framework The hush Framework The San Francisco Framework

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

17. vrije Universiteit amsterdamPostacademische Cursus Informatie Technologie The Unified Modelling Language use case diagram class diagram behaviour diagrams: –state-chart diagram –activity diagram –interaction diagrams: sequence diagram collaboration diagram implementation diagrams: –component diagram –deployment diagram For some background see: Ch. 11: Methods and Tools

18. 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

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29. 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

30. vrije Universiteit amsterdamPostacademische Cursus Informatie Technologie Frameworks Frameworks = Components + Patterns Ralph Johnson, CACM Nov. 1997 Self-documentation Principle Bertrand Meyer, OO Software Construction 2nd ed. the designer of a module should strive to make all information about the module part of the module itself...

31. vrije Universiteit amsterdamPostacademische Cursus Informatie Technologie The benefits The benefits of frameworks stem from the inversion of control. A Framework defines an Architecture?

32. 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

33. 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

34. 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

35. 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

36. 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

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

38. vrije Universiteit amsterdamPostacademische Cursus Informatie Technologie Java If Java is the Answer, What is the Question? see Ted Lewis, IEEE Computer, March 1997, p. 136

39. vrije Universiteit amsterdamPostacademische Cursus Informatie Technologie The dream: UNCOL Java is pervasive remember, most of Java is just warmed-up C/C++ UNCOL = Universal Common Language (1963) Algol -> PL/I -> Pascal -> Ada -> C++ -> … Java as UNCOL: the dial-tone of the Internet if today's languages are inadequate for Software then Java must be inadequate too...

40. vrije Universiteit amsterdamPostacademische Cursus Informatie Technologie Hostages of legacy code our responsibility is that future applications (built with Java) are well-behaved legacy systems US DOD: $ 30 billion in year 2000 problem maintaining legacy COBOL from the 70's is a major industry... by 2010, Java will be the maintenance tail wagging the software dog!

41. vrije Universiteit amsterdamPostacademische Cursus Informatie Technologie Is Java doomed to repeat history? elegant minimalism is one of the goals of Java, remember Pascal, a toy language! Java lacks IO, OS support...

42. vrije Universiteit amsterdamPostacademische Cursus Informatie Technologie Problems Java = watered-down C++, retrofitting Pascal –syntax: int i = ++i--; –unruly scope rules: C++ plus f i n a l, n a t i v e, s y n c h r o n i z e d,... –threads: potential deadlocks

43. vrije Universiteit amsterdamPostacademische Cursus Informatie Technologie Java: a better mousetrap? requirements: no support (assert) defacts: syntax, non-standard APIs components: Beans  ActiveX, CORBA, OpenDoc cycle time: Java does little to accommodate Internet time, like script languages do complexity: Java does not advance the intellectual frontier!

44. 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 and see frameworks

45. 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

46. vrije Universiteit amsterdamPostacademische Cursus Informatie Technologie Risk Reduction Strategies Knowledge –clear the fog -- get to the real issues –early and regular delivery -- discover what you don't know –prototype! -- discover how it really works –create microcosm -- do something real, but with care

47. vrije Universiteit amsterdamPostacademische Cursus Informatie Technologie Risk Reduction Strategies Teaming –holistic diversity -- co-ordinate specialists! Productivity –gold rush -- start immediately, adjust slowly Ownership – function / component owners -- create responsibility

48. vrije Universiteit amsterdamPostacademische Cursus Informatie Technologie Risk Reduction Strategies Distractions –someone always makes progress -- no total interruption –team per task -- a subteam deals with diversions –sacrifice one person -- and preserve the team Training –day care -- hire an expert to take care of novices

49. 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

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

51. 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.

52. 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