1. Finishing up on Methods (or the last bit of JSD and the other methods in brief)

2. 2 JSD Implementation In essence we must transform the concurrent specification we have developed into a sequential one. Then we start coding. We do the transformation by means of process inversion.

3. 3 Process Inversion Replace data stream connections by CALL & RETURN instructions Hence: Becomes: Then we write a SCHEDULER process A B A B

4. 4 Now read the notes Of course, there’s more to it than that, but you can read the book/notes for the details yada yada yada blah blah blah Yoda, Yoda, Yoda, Jedi, Jedi, Jedi...

5. More Methods YSM, STRADIS, SSADM, Information Engineering

6. 6 Yourdon Systems Method Read the books for details, but essentially: A functional decomposition approach Though it claims to be “middle out”. Uses DFDs, STDs, etc.

7. 7 YSM Features Based around a set of models which abstract the main features of what is under examination and then present those features in a useable way Enterprise Model System Essential Model

8. 8 Enterprise & System An enterprise is an economic unit that is resourced and managed as a unit A system is a collection of information and operations that are organised to meet a specific problem. –Enterprise is not a system. Has a longer life-span than a system. Within an enterprise, several systems may be developed, used and replaced.

9. 9 Viewpoints of a System YSM takes 3 orthogonal viewpoints: –Function: what the system does. DFDs are used here. –Time: what happens and when (Use an Event List that shows what happens to which system must respond). –Information: what information is used by the system. (use ER models for this)

10. 10 STRADIS Gane & Sarson worked with Yourdon in early years hence there is some similarity between these methods. Concerned mainly with systems analysis, to a lesser extent with systems design and hardly at all with implementation. Uses Functional Decomposition

11. 11 Method Stages The initial study The detailed study Defining and designing alternative solutions Physical design What do we notice about steps 1-3?

12. 12 Rationale Wide applicability in the area of information systems Most relevant to a situation in which there is a backlog of systems waiting to be developed and insufficient resources to devote to all potential new systems Incorporates a wide variety of established techniques

13. 13 Information Engineering Based on work of Finkelstein and James Martin Associates A BIG method Tends to be used by large organisations for strategic IS development projects

14. 14 Rationale Main problem is viewed as the provision of information, not the construction of software The basis of the I.S. is data because this is more stable than processes or procedures The most appropriate means of communication is through diagrams

15. 15 Stages The method has LOTS of stages and steps Not all projects will require all stages Uses functional decomposition, but with a twist

16. 16 SSADM Good grief, what can we say? H.M. Government standard since 1983 Straightforward F.D. method Does not address implementation Version 4 uses FPA Drone, drone, drone, drone.. Droid, droid, droid, C3PO...

17. 17 Methods X,Y & Z And there are many others besides. So, what do we do with it all? Watch this space...