Systems Analysis and Design ISQA 420 Fall 2001 Sept. 26 “Basic concepts and terms”

1. Systems Analysis and Design ISQA 420 Fall 2001 Sept. 26 “Basic concepts and terms”

2. SYSTEMS ANALYSIS & DESIGN o In great part, it’s about understanding and representing business processes... o … in ways that can help in building information systems that can solve real business problems. o It involves answering two fundamental questions: What systems should we develop? What, especially from the users’ perspective, should those systems do and how should they do it?

3. WHAT’S AN INFORMATION SYSTEM? o “A system is a set of interrelated components that work together in a particular environment to perform whatever functions are required to achieve the system’s objective.” Components: people, procedures, data, software, and hardware (PPDSH). Functions: input, processing, output, storage, and control (IPOSC) Plus, a third view: A system is comprised of subsystems.

4. Manual or automated Automated IS – people/procedures/data/software/hardware – PPDSH System – environment – organization contexts Information System

5. Object-oriented approach Object – thing, event, person, place, transaction Class - A category – set of objects sharing attributes & common functions Attribute. A characteristic of a class. Method - something an object “knows how to do” that relates to its own data. – function, Operations, behavior Instance and Object. An individual member of a class (either for real, or the real instance’s representation in/by the information system).

6. Message - How one object asks another to do something, or how it responds to such a request. Inheritance – subclass and superclass Business objects – Bank, manufacturing facility Object-oriented approach

7. Phases – Development/Conversion/Production Systems approach – problem solving method breaks a complex problem into pieces design a solution for each piece Integrates solution into a complete system Reduces complexity Increases likelihood of each aspect of the problem to be solved are fully considered Decompose problem in subsystems – analyze each subsystem & the way it interacts with other subsystems Hasbro – import tracking (shipment tracking, Import duty processing) SDLC and system approach

8. Two activities – analysis & design Analysis – study existing system Purpose Understand components and functions of current system Identify organizational information and processing needs Determine characteristics of new system to meet these Design – process of synthesizing or reassembling the components & functions identifies during analysis Purpose Specify component & function of system that will be efficient & effective in meeting an organizational information needs Alternative solutions – select one – design in detail – design specs “blueprint” used to construct the system Systems approach

9. System decomposition Three ways to decompose By functions – IPOSC By components – PPDSH By systems - accounting -> payroll/sales order processing/AR/inventory control/AP Systems Analysis

10. TSD and OS&BA TSD – functional decomposition Process duty payments Verify shipment receipt Determine shipment produce category Calculate import duty Generate import duty OS&BA - system decomposed into objects and how they interrelate Identify business objects Create object model – describing class attributes, methods, & relationships SD paradigms

11. TSD Focuses on verbs Functions performed on data Separate software and data components OO&BA On nouns Objects performing functions Combines data & software into a single object class Comparison

12. Enterprise model – graphically represents organizational entities & relationships between Modeling techniques – affinity diagram, work flow diagram Process model - graphically represents of a systems functions - DFD/ program structure charts Data model - graphically represents system’s data & relationship between data element – ERD Object model - graphically represents system in terms of classes with attributes/methods/relations Four categories of models

13. Computer Aided Software Engineering/Computer Aided Systems Engineering CASE tools CASE

14. SYSTEMS CATALYSTS User demand o system errors o system efficiency o system compatibility o system enhancements Technology push … the decision to innovate precedes the business problem-solving activity. Strategic pull Note: User demand and strategic pull don’t always match!

15. ` SYSTEM GOALS (AND EVALUATION) System Quality o Functionality (reliability, clarity, efficiency) o Maintainability (documentation, modularity) o Flexibility (adaptability, portability) Organizational Relevance o Efficiency o Effectiveness o Competitive Advantage Project Management o Timeliness o Cost o Client Commitment

16. Systems Analysis and Design ISQA 420 Fall 2001 Product of Systems Development

17. Logical functions (enter data item) – physical functions (scan product) Input – processing – Output functions – figure 2.2 Input – accept, receive, enter, read Processing –calculate, sort, compare, summarize – OAS, TPS, MSS Output - distribute, produce, write, display Storage – CRUD – create, read, update, delete Control – General controls/ application controls – hardware/software Input, processing, output controls IS Functions

18. Computer system – hardware/software People: user, designer, implementer Procedures – informal (organizational culture) / formal Control procedures - Application procedures - System procedures – how to operate Data – input, stored, output data (figure 2.5) DBMS Technology – hardware/software – System software, application software, 4th GL, workflow – Computers, peripherals, telecom Documenting IS components – function/component matrix. – Table 2.4 IS Components

19. Systems Analysis and Design ISQA 420 Fall 2001 Methodologies

20. “Methodology”… A systematic specification of the sequence of activities required to solve a problem. Any systems development methodology demands three different activities: o analysis o design o implementation The essential differences arise in how those activities are accomplished: o purely sequential (“lockstep”)? o iterative?

21. Traditional systems development (the “waterfall” approach)...

22. Efforts to improve the responsiveness of systems development... JAD (Joint Application Design) RAD (Rapid Application Development) Phased development Prototyping Important to note: These are not mutually exclusive!

23. The “Bridge” Methodology...

24. Analysis & design of data structure, system behavior, and interfaces… System data structure o What: object classes, their attributes, their relationships o How: object-relationship models, data models, E-R diagrams, class diagrams System behavior o What: . . .

25. System behavior: a conventional implementation…

26. System behavior: an OO implemen- tation…

27. Analysis & design of data structure, system behavior, and user interfaces… System data structure o What: object classes, attributes, relationships o How: object-relationship models, data models, E-R diagrams, class diagrams System behavior o What: programs acting on data (conventional) objects employing methods (OO) o How: DFDs, structure charts, structured English, etc. (conventional) use cases, class diagrams (OO) User interfaces o What: dialog, form, report, menu, icon, etc. o How: use cases, dialog flow diagrams, state transition charts