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LIS1510 Library and Archives Automation Issues Systems Analysis

LIS1510 Library and Archives Automation Issues Systems Analysis. Andy Dawson School of Library, Archive & Information Studies, UCL (University of Malta 2008). What we will be looking at today. The lifecycle concept The need for good analysis Describing the system Identifying the needs

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LIS1510 Library and Archives Automation Issues Systems Analysis

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  1. LIS1510Library and Archives Automation IssuesSystems Analysis Andy Dawson School of Library, Archive & Information Studies, UCL(University of Malta 2008) Andy Dawson

  2. 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

  3. The system life cycle (from yesterday) • Analysis • Design • Implementation • Evaluation • Decay • Replacement

  4. The systems development lifecycle • Strategic study • Feasibility study • Physical systems analysis • Logical systems definition • Logical systems design • Physical systems design • Implementation • Maintenance

  5. Or more simply • (Requirements) analysis • Design • Implementation • Maintenance

  6. The PARIS model • Plan • Ask • Record • Interpret • Specify

  7. As we said yesterday... • Why do so many systems seem to “fail”? • Misapprehension • Miscommunication • Misinterpretation • Misidentification • Misrepresentation

  8. 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. Requirements Analysis • Identify elements • Model elements • Verify • Importance of Conceptual Modelling -Independence from physical implementation

  10. 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. How do we do this? • A process of expansion & contraction • Decomposition • Synthesis • Identifying and relating static & dynamic elements • Facts • Processes

  12. 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. 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. Key elements and considerations • Relationship to other models • Components • Sources/sinks (external entities) • Processes • Data stores • Data flows

  15. Symbology/notation • Importance of notation • Data flows between sources/sinks/stores via processes which transform the data • SSADM notation

  16. SSADM context diagram

  17. SSADM notation - first level DFD

  18. SSADM notation - second level DFD

  19. Naming • Importance of naming • Sources/sinks: generic descriptive • Stores: simple descriptive • Processes: “imperative action” concept • Flows: what is tranferred • Avoid ambiguity

  20. Hierarchies • Concept of levelling • Top-down decomposition • Practical levelling • Balancing • Ensure all inputs and outputs balance (match) across the levels of the hierarchy

  21. 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. 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. Refining and developing the diagram • Iterative process! • Importance of • Balancing • Naming • Controlling complexity • Document flow diagrams • Data models

  24. After the break: A brief exercise in process modelling!

  25. That’s all for today! • Any questions? • Tomorrow: • Wrapping up the lifecycle • Feasibility studies and operational requirements • Systems selection and installation

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