Sept 2007 K. Ingram 1 Waterfall Life Cycle An introduction to the Waterfall

Sept 2004 K. Ingram 2 Contents Reminder of what you have already done General steps for Software Development Project Plans The Waterfall Life Cycle

Sept 2004 K. Ingram 3 What you have already done The Level 1 module: CE Business Systems Analysis, Design and Construction /StartFrameSet.htm /StartFrameSet.htm This used the structure:  Investigation  Analysis  Design, Development and Testing  Hand over to client (actually to tutor!)

Sept 2004 K. Ingram 4 General Steps for Software Development 1. Get necessary facts 2. Ensure facts not ambiguous/conflicting and no information missing 3. Work out how to do it 4. Do it 5. Check it 6. Hand it over to users

Sept 2004 K. Ingram 5 How to ensure it all gets done right Monitor progress Monitor quality Make adjustments if necessary These all need a PLAN to monitor against!

Sept 2004 K. Ingram 6 Waterfall Project Plan (example) OctNovDecJanFebMarchAprilMay Establish Require’ts Fact-finding Analysis Design Development Testing Implement Review/ Appraisal

Sept 2004 K. Ingram 7 Waterfall Life Cycle Assumes that ALL of the project is handled at each stage e.g.  ALL requirements are identified at the start  ALL the system is analysed  ALL the system is designed  ALL the system is written  ALL the system is tested  ALL the system is handed over to the client  etc So there is only 1 run through the life cycle

Sept 2004 K. Ingram 8 Waterfall variations You will see many slight differences in the names of steps in the waterfall life cycle in different books/from different people. Don’t get too hung up on those details – the Waterfall concept will be the same. There are Life Cycles which are not Waterfall and we will look at those separately.

Sept 2004 K. Ingram 9 Some Advantages of the Waterfall Life Cycle Known requirements are all documented Analysis can cover all required areas Design can be optimised as all known requirements are included Coding and testing can be carried out efficiently as all areas to be covered are known. Project management is easier as tasks required are known – timetables and staffing can be:  planned  controlled

Sept 2004 K. Ingram 10 Some Disadvantages of the Waterfall Life Cycle What if the client think of important requirements later in the project? What if the client’s requirements change during the project? What if a step in the project takes longer than expected? What if the client does not like what the developers have produced? What if the system handed over to the client does the wrong thing?

Sept 2004 K. Ingram 11 Summary The Waterfall Life Cycle goes through a life cycle once. At each stage it handles all the known requirements. It has advantages and disadvantages. This means it is very suitable for certain situations and unsuitable for other situations.

Sept 2004 K. Ingram 12 Review Questions 1. Identify 5 advantages of having a project plan. 2. Would you describe the waterfall life cycle as ‘flexible’ or ‘inflexible’? Why? 3. Under what circumstances would a waterfall life cycle be a:  good choice?  bad choice?