1. DEPARTMENT OF INFORMATION STUDIES Andy Dawson LIS1510 Library and Archives Automation Issues Systems Analysis Andy Dawson Department of Information Studies, UCL Department of Information Studies, UCL (University of Malta 2010)

2. DEPARTMENT OF INFORMATION STUDIES Andy Dawson What we will be looking at today The lifecycle concept The need for good analysis Describing the system Identifying the needs Practical exercise – process modelling Second coursework issued

3. DEPARTMENT OF INFORMATION STUDIES Andy Dawson Analysis Design Implementation Evaluation Decay Replacement The system life cycle (from yesterday)

4. DEPARTMENT OF INFORMATION STUDIES Andy Dawson The systems development lifecycle Strategic study Feasibility study Physical systems analysis Logical systems definition Logical systems design Physical systems design Implementation Maintenance

5. DEPARTMENT OF INFORMATION STUDIES Andy Dawson Or more simply (Requirements) analysis Design Implementation Maintenance

6. DEPARTMENT OF INFORMATION STUDIES Andy Dawson The PARIS model Plan Ask Record Interpret Specify

7. DEPARTMENT OF INFORMATION STUDIES Andy Dawson As we said yesterday... Why do so many systems seem to “fail”? Misapprehension Miscommunication Misinterpretation Misidentification Misrepresentation

8. DEPARTMENT OF INFORMATION STUDIES Andy Dawson The role of Systems Analysis Systems analysis allows/helps us to: –identify systems –break them down –make them work (better) Good systems analysis helps organisations to succeed Necessary precursor to proper system selection

9. DEPARTMENT OF INFORMATION STUDIES Andy Dawson Requirements Analysis Identify elements Model elements Verify Importance of Conceptual Modelling - Independence from physical implementation

10. DEPARTMENT OF INFORMATION STUDIES Andy Dawson The focus of analysis Systems tend to be Data-based or Process-based (transactional) Transactions deal with transformations of data, input and output Therefore we need to identify & develop transactions and data, and their interaction with the environment, to analyse a system

11. DEPARTMENT OF INFORMATION STUDIES Andy Dawson How do we do this? A process of expansion & contraction –Decomposition –Synthesis Identifying and relating static & dynamic elements –Facts –Processes

12. DEPARTMENT OF INFORMATION STUDIES Andy Dawson The value of models Why do we model? –To improve clarity and accessibility –To show different relational aspects of the system –To help understanding Different types of model –Data-based & Process-based –Varieties of model –Completeness of view

13. DEPARTMENT OF INFORMATION STUDIES Andy Dawson Process modelling – The data flow diagram Basic process modelling tool –full-scale analysis involves multiple models –different tools are used for data modelling etc Top-down approach Valuable for describing –current physical system –logical/desired system Helps us to grasp system as a whole

14. DEPARTMENT OF INFORMATION STUDIES Andy Dawson Key elements and considerations Relationship to other models Components –Sources/sinks (external entities) –Processes –Data stores –Data flows

15. DEPARTMENT OF INFORMATION STUDIES Andy Dawson Symbology/notation Importance of notation Data flows between sources/sinks/stores via processes which transform the data SSADM notation

16. DEPARTMENT OF INFORMATION STUDIES Andy Dawson SSADM context diagram

17. DEPARTMENT OF INFORMATION STUDIES Andy Dawson SSADM notation - first level DFD

18. DEPARTMENT OF INFORMATION STUDIES Andy Dawson SSADM notation - second level DFD

19. DEPARTMENT OF INFORMATION STUDIES Andy Dawson Naming Importance of naming Sources/sinks: generic descriptive Stores: simple descriptive Processes: “imperative action” concept Flows: what is tranferred Avoid ambiguity

20. DEPARTMENT OF INFORMATION STUDIES Andy Dawson Hierarchies Concept of levelling –Top-down decomposition –Practical levelling Balancing –Ensure all inputs and outputs balance (match) across the levels of the hierarchy

21. DEPARTMENT OF INFORMATION STUDIES Andy Dawson Referencing/numbering Basic principles –Decimal heirarchies Lower case lettering for entities Mn/Dn stores Stores within processes Single/double flow lines and direction Multiple sources/sinks/stores Process locations/roles (physical)

22. DEPARTMENT OF INFORMATION STUDIES Andy Dawson Constructing data flow diagrams Follow the top-down approach Define boundary (context diagram) Identify –Static components –Key processes –Flows between them Build -expand - refine - review

23. DEPARTMENT OF INFORMATION STUDIES Andy Dawson Refining and developing the diagram Iterative process! Importance of –Balancing –Naming –Controlling complexity Document flow diagrams Data models

24. DEPARTMENT OF INFORMATION STUDIES Andy Dawson After the break: A brief exercise in process modelling!

25. DEPARTMENT OF INFORMATION STUDIES Andy Dawson That’s all for today! Second coursework Any questions? Tomorrow: –Wrapping up the lifecycle –Feasibility studies and operational requirements –Systems selection and installation