Critical Issues in Information Systems

1. Critical Issues in Information Systems BUSS 951 Lecture 4 Design 1: Technical and Methodological Aspects

2. Notices (1)General • Make sure you have a copy of the BUSS951 Subject Outline • BUSS951 is supported by a website (available from Tomorrow), where you can find out the latest Notices and get Lecture Notes, Tutorial Sheets, Assignments etc www.uow.edu.au/~rclarke/buss951/buss951.htm • Pick up assignment 1 now! • Note there has been a change in the Lecture schedule we will move lectures 8->4 and 9->5

3. Notices (2)Readings for Week 4 • Watson, Rainer and Koh (1991) “Executive Information Systems: A Framework for Development and a Survey of Current Practices” We use this paper as an example of applying the kind of analysis needed for your assignment

4. Agenda (1) • Organisational Metaphors • Machines • Organisms • Specific Organisational Theories • Complex Organisations • Network Organisations • Population Ecology Models

5. Life Cycles

6. What is a Life Cycle? (1) • Life Cycles are generalisations of the steps or phases leading to the development of an IS • emerged from fields of evolutionary biology and cybernetics • models of software evolution date back to the earliest projects developing large software systems (circa 1956)

7. What is a Life Cycle? (2) • provide an abstract scheme accounting for the ‘natural’ or engineered development of systems • simplify the actual steps or development work practices found in real methodologies

8. What is a Life Cycle? (3)Needs served • planning, organising • staffing, coordinating • budgeting, and • directing software development activities

9. What is a Life Cycle? (4)Prescriptive Life-cycles • describe how systems should be developed (generally as a set of steps) • easier to describe, however many software development details are ignored

10. What is a Life-Cycle? (5)Descriptive Life Cycles • characterise how systems are actually developed • much less common; more difficult to describe because data must be collected throughout systems life • system specific • therefore, prescriptive models are dominant

11. Life Cycles & System Change (1)Two distinct views • life cycles suggest ways in which a system changes or evolves over time • two distinct views on systems change: • evolutionist models • evolutionary models

12. Life Cycles & System Change (2)Evolutionistic Models • describe system change as progress through a series of stages eventually leading to some final stage • useful as organising frameworks for managing development effort • poor predictors of why certain changes are made to a system & why systems evolve in specific ways

13. Life Cycles & Systems Change (3)Evolutionary Models • focus attention to the mechanisms and processes that change systems • less concerned with stages of development and more with the technological mechanisms and organisational processes that change systems over space and time

14. How many Life-Cycles? (1) • Very much smaller number of life cycles than actual methodologies • In rank order of popularity: • SDLC (Systems Development Life Cycle) • RPLC (Rapid Protoyping Life Cycle) • EDLC (Evolutionary Development Life Cycle) • Others (Whirling, Curriculum)

15. SDLC

16. SDLC Initiation Analysis Maintenance & Evaluation Operation & Acceptance Design Construction

17. Analysis Design Design Construction Initiation Initiation SDLCB-Model Development Path Construction Acceptance Maintenance Cycle Operation Design Evaluation Initiation Analysis

18. Benefits of SDLC (1)Some Advantages • traditional SDLC has brought a much-needed discipline to systems development • much better to use SDLC than not to use any approach! • can be used to create successful systems

19. Benefits of SDLC (2) • fits in with structured techniques • structured programming: use of restricted control structures: sequence, selection, repetition • structured design: cohesion- one & only one function- and coupling- minimal dependency of modules • structured analysis: Yourdon and DeMarco, Gane and Sarson- data flow (which is actually process oriented view

20. Problems with SDLCDocument Driven Development • SDLC is document driven • each stage usually has a specific deliverable (often a document) used at a subsequent stage • reflected in the Computer Aided Software Engineering tools (CASE) used to support SDLC

21. Problems with SDLCSome Flaws... • implementation begins after requirments and design documents have been completed • if the system specification is complete and the design is of high quality, implementation will probably be straight forward

22. Problems with SDLC...Some Flaws • however, system design is often flawed • important design decisions must be made during implementation • specification and design errors not identified during implementation are built into the system

23. Problems with SDLCUsers • pre-specifying user requirements prior to development of IS is difficult • traditional deliverables are poor communication tools • users often do not know what they want until they can see a working model

24. Problems with SDLCUsers • user involvement in the requirements definition and reviews of overall system design do not guarantee user satisfaction • users are often disappointed with the completed system

25. Problems with SDLCUsers • traditional pre-specification methods often don’t help in many user-oriented applications • decision support systems • data base applications • particularly when requirements and decision processes are unclear

26. Increasing UncertaintyUser Requirements Levels Systems Strategic Management • Management Information Systems • Executive Information Systems • Decision Support Systems • Information Reporting Systems • Operations Information Systems • Office Automation Systems • Transaction Processing Systems • Process Control Systems Tactical Management Operational Management Business Operations Increasing Uncertainty in System Requirements

27. Prototyping: Rapid & Evolutionary

28. Types of PrototypingRapid versus Evolutionary • prototype is discarded as a new production system is constructed using another language (Rapid Prototyping or Type II) • the basis for full-scale development of the production system (Evolutionary Prototyping or Type 1)

29. Develop Prototype Analysis Test Prototype Design Amend Prototype Construction RPLC Investigation Maintenance & Evaluation Operation & Acceptance

30. Develop Prototype Test Prototype Amend Prototype EDLC

31. Problems with Prototyping • inappropriate, incomplete, and inadequate analysis and design • unrealistic performance expectations • poorly controlled projects • reluctance to discard prototype models • problems with users

32. Problems with Prototyping • does not necessarily improve productivity in all phases • can involve risks but these can be avoided if careful planning and project management are used

33. Experimental Life Cycles: Spiral & Curriculum

34. Design Construction SLCSpiral Life Cycle Investigation Maintenance & Evaluation Analysis Operation & Acceptance

35. CLCCurriculum Life Cycle Deconstruction Joint Construction Social Setting Independent Construction

36. Methodologies

37. Life Cycle Methodologies Life Cycles & Methodologies Use prescriptive life cycles to explain and compare between real methodologies

38. Classes of Methodology Data-oriented IE (Martin & Finkelstein) JSD (Jackson) Process-oriented STRADIS (Gane and Sarson) SSADM (Learmonth & Burchett) Rapid Prototyping Softwright Systems JAD Human-centred ISAC (Lundberg) ETHICS (Mumford) SSM (Checkland) Evolutionary Prototyping Milton Jenkins Systemscraft (Crinnion)

39. What are Methodologies? • Any methodology must support two components: • toolsand methods for recording & analysing the existing system, new users requirements, specifying the format of the new system • an overall framework, indicating which tools are to be used at which stages in the development process

40. Adaptive Methodology • can tailor to the client organisation • can tailor to the IT developers • can tailor to the individual project • this feature is called adaptiveness

41. Adaptive Methodology • delete (jettison) unneeded methods • addition of needed methods • Controls Analysis Technique (CAT) • Quality Control Method(s)

42. Adaptive Methodology • exchange semantically similar techniques • changing deMarco DFDs for Gane & Sarson DFDs • exchange functionally similar techniques • Chen ERDs for Merise ERDs • Hawryskiewicsz NFs for Finklestein BNFs

43. Scalable Methodologies • Systemscraft is a scalable methodology • Scalability is a kind of adaptability • centres on the deletion (jettisoning) or addition of methods

44. Scalable Methodologies • depends on the size and complexity of development projects • but might need other methods to cope with aspects of complex projects • or to enforce rigour on large projects

45. Designing Systems

46. Design Problemscannot be completely stated (1)... • never know when all aspects of the problem emerged- some may never be fully uncovered • generated by groups with different involvements • some problems only emerge when attempts are made to generate solutions

47. Design Problemscannot be completely stated (2)... • full of uncertainties both in terms of objectives, priorities • objectives, priorities likely to change during the process • shouldn’t expect static, complete formulation of design problems • problems-solutions in tension

48. Design Problemsrequire subjective interpretation (1)... • designers likely to devise different solutions, perceive problems differently • understanding problems depends to an extent on our ideas for solving • managers see problems as management problems etc/

49. Design Problemsrequire subjective interpretation (2)... • difficulties with measurement in design • problems are inevitably value-laden, therefore solutions are based on subjective perception • don’t expect entirely objective formulations of design problems

50. Design Problemsorganised heirarchically (1)... • design problems can often be viewed as symptoms of other ‘higher-level’ problems • eg/ building a tourist resort • waste water- a problem for plumbers • a problem for tourist organisations • a problem for environmentalists • a problem for government policy makers