6 Software Lifecycle Models.ppt

6. Software Lifecycle Models A software lifecycle model is a standardised format for planning organising, and running a new development project. Hundreds of different kinds of models are known and used. Many are minor variations on just a small number of basic models. In this section we: survey the main types of model, and consider how to choose between them. 6.1. Planning with Models SE projects usually live with a fixed financial budget. (An exception is maintainance?) Additionally, time-to-market places a strong time constraint. There will be other project constraints such as staff. Project planning is the art of scheduling the necessary activities, in time, space and across staff in order to optimise: project risk [low] (see later) profit [high] customer satisfaction [high] worker satisfaction [high] long-term company goals Questions: 1. What are these necessary activities? (besides programming) 2. Are there good patterns of organisation that we could copy? A project plan contains much information, but must at least describe: resources needed (people, money, equipment, etc) dependency timing of work (flow graph, work packages) rate of delivery (reports, code, etc) It is impossible to measure rate of progress except with reference to a plan. In addition to project members, the following may need access to parts of the project plan: Management, Customers Subcontractors Suppliers Investors Banks 6.2. Project Visibility Unlike other engineers (e.g. civil, electronic, chemical … etc.) software engineers do not produce anything physical. It is inherently difficult to monitor an SE project due to lack of visibility. This means that SE projects must produce additional deliverables (artifacts) which are visible, such as: Design documents/ prototypes Reports Project/status meetings Client surveys (e.g. satisfaction level) 6.3. What is a Lifecycle Model? Definition. A (software/system) lifecycle model is a description of the sequence of activ