McConnell Lifecycles.ppt

							Chapter 7

       Lifecycle Planning




                            1
Lifecycles - Introduction
   A lifecycle model is a prescriptive model of what should happen
    between the first glimmer and the last breath of a (software)
    project

   It establishes the order in which a project specifies, prototypes,
    designs, implements, reviews, tests, and performs other
    activities

   Choosing a lifecycle for a project has the same influence over
    the success of a project than any other planning decision made

   The right choice can streamline your project and help to
    approach your goal in a sequence of successful steps

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             continued …




Source: Introducing Systems
Analysis, Steve Skidmore, 1997


                                 3
continued …
   Strategic study
        Define possible IS contributions to the objectives of the enterprise
        Identification of candidate applications


   Feasibility study
        Examination and comparison of candidate applications
              Economic, technical, operational issues
        Output: feasibility report
              Recommends possible solution and comments whether detailed analysis should commence
              From this detailed systems project are initiated


   Physical systems analysis
        Start of a detailed systems investigation of the current system and the requirements of
         its successor
        Output: requirements analysis document



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continued …
   Logical systems definition
        Development of required system (models for data, processes and events)
        Output: requirements specification document

   Logical systems design
        Logically defining data structures (normalisation), and definition of detailed processes
        Output: logical design document

   Physical systems design
        Development of physical inputs and outputs, e.g., files, programs, databases
        Output: physical design

   Implementation
        Testing of programs and systems, development of support manuals and
         documentation, training courses, phasing in of the new system into the organisation

   Maintenance
        Implementation of amendments and omissions, new requirements, new hard/software

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            Pure Waterfall




Source: Rapid Development - Taming Wilde
Software Projects, McConnell, 1996
                                           6
continued …
   Basis for most models (starting point)
   Orderly sequence of steps
        Review at the end
        Does not proceed until goals are met
        Phases do not overlap
   Document driven
   Works well
        Stable product definition
        Well understood, complex problems
        All planning is done upfront
        Quality dominates cost and schedule
        Technically weak staff
   Disadvantages
        Poor visibility
        No tangible results until the end
        Sensitive to midstream changes
        Not flexibility
        Usually it is not possible to fully specify requirements at the start (before any design)
   In reality activities often overlap
                                                                                                     7
            Salmon Waterfall Model




Source: Rapid Development - Taming Wilde
Software Projects, McConnell, 1996
                                           8
Code-And-Fix

            System Specification                    Release
                                   Code and Fix
                 (maybe)                            (maybe)




   Quite common
   Jump straight into coding
   If you don’t use any lifecycle model you are probably using code-and-
    fix
   Combined with short schedules it may lead to code-like-hell
   Advantage
        No overhead, may work for small projects



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            Spiral




Source: Rapid Development - Taming Wilde
Software Projects, McConnell, 1996
                                           10
            Modified Waterfall - Sashimi




Source: Rapid Development - Taming Wilde
Software Projects, McConnell, 1996
                                           11
            Waterfall With Subprojects




Source: Rapid Development - Taming Wilde
Software Projects, McConnell, 1996
                                           12
            Waterfall With Risk Reduction




Source: Rapid Development - Taming Wilde
Software Projects, McConnell, 1996
                                           13
            Evolutionary Prototyping




Source: Rapid Development - Taming Wilde
Software Projects, McConnell, 1996
                                           14
            Staged Delivery




Source: Rapid Development - Taming Wilde
Software Projects, McConnell, 1996
                                           15
            Design-To-Schedule




Source: Rapid Development - Taming Wilde
Software Projects, McConnell, 1996
                                           16
            Evolutionary Delivery




Source: Rapid Development - Taming Wilde
Software Projects, McConnell, 1996
                                           17
            Design-To-Tools




Source: Rapid Development - Taming Wilde
Software Projects, McConnell, 1996
                                           18
Commercial Of-The-Shelf
Software
   May not satisfy all your needs but

   Immediately available

   Often cheap, e.g., no costs for design, development

   Software product can be built around the functionality provided by a
    tool

   Free time for more important tasks

   Some functionality immediately available – good for customer feedback



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