System Engineering and Analysis

1. System Engineering and Analysis “What is the role of the software product?” TCS2411 Software Engineering

2. Lecture Objectives • To examine the elements of a computer-based system • To understand the development process of a system • To illustrate the representations of a business information system TCS2411 Software Engineering

3. Definition of System “A collection of interrelated components that work together to achieve some objective” Objective: to develop a product, to support business functions…etc. TCS2411 Software Engineering

4. Data Process Information Information system types • Manual (read a text by your eyes then summarize using your pen) • Automated (get the information through a computerized system) TCS2411 Software Engineering

5. system environments • Internal, like users, organization structure and procedures • External, consists of all factors outside the organization that affect the system TCS2411 Software Engineering

6. System Elements • Software: computer programs, data structures, and related documents. • Hardware: electronic computing devices and connectivity devices. • People: users and operators. • Database: large and organized collection of information that is accessed via the software. • Documentation: descriptive information for user and operator (e.g. hardcopy manuals, on-line help files) • Procedures: steps that define the specific use of each system element. TCS2411 Software Engineering

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8. System Life Cycle Phases • Initial Strategy • Identification of needs, problems, opportunities, goal objectives and scope. • Critical to the success of the project. • The analyst must be honest. • The analyst must discover what the business is trying to do. TCS2411 Software Engineering

9. System Life Cycle Phases (Continued) • Determining the Requirements (Information and Tools) • Several tools are used to define IR in the business, sampling, investigating of hard data, interviewing, questionnaires, observing, prototyping. • The analyst is striving to understand what information users need to perform their job TCS2411 Software Engineering

10. System Life Cycle Phases (Continued) • Feasibility Study • Economic, technical, legal feasibility (can be done or not). • Cost-benefit analysis, risk assessment • "Go / no-go" decision • Analysis • Requirements definition & specification • there are some special tools and techniques that help the analyst as DFD, Data Dictionary TCS2411 Software Engineering

11. System Life Cycle Phases (Continued) • Design • Logical & Physical Design (Design the interface, input/output, file or database) • System specifications • Implementation • Installation • Training • File conversion • Systems testing, security TCS2411 Software Engineering

12. System Life Cycle Phases (Continued) • Maintenance, Review and Test • Amendments (fix) by the programmers • System audit, by the programmers and analyst TCS2411 Software Engineering

13. System Engineering Hierarchy Business or product domain Domain of interest World view System element Domain view Element view Detailed view TCS2411 Software Engineering

14. System Engineering Hierarchy continue • World view: the entire business or technology is examined. • Domain view: specific domain of interest. • Element view: the need for targeted system element (e.g. data, software, hardware, people) is analyzed. • Detailed view: analysis, design, and construction of a targeted system element. TCS2411 Software Engineering

15. System Modeling The engineer creates models that: • define processes for the view under consideration. • represent behaviour of the processes • explicitly define exogenous and endogenous input to the model • represent all linkages (including output) to better understand the view TCS2411 Software Engineering

16. Exogenous & Endogenous Inputs • Exogenous inputs link one constituent of a view with other constituents (at the same or other levels) • Endogenous inputs link individual components of a constituent at a particular view TCS2411 Software Engineering

17. Restraining Factors of System Model • Assumptions • Simplifications • Limitations • Constraints • Preferences TCS2411 Software Engineering

18. Enterprise Modeling • Organizational structure • Business-level data modeling • Process modeling • Information flow modeling TCS2411 Software Engineering

19. Organizational Structure XYZ Company Corporate Support Sales & Marketing Engineering Manufacturing ….. Finance Planning TCS2411 Software Engineering

20. Business-level Data Modeling describes Product A Salesperson sells purchases contacts Customer evaluates assists inquires about TCS2411 Software Engineering

21. Process Modeling Establish customer contact Prepare delivery order Provide product info Check availability Provide evaluation product Address questions/ concerns Accept sales order TCS2411 Software Engineering

22. Information Flow Modeling Contact record Establish customer contact Prepare delivery order Product info Provide product info Product description Customer d.o. info Check availability Provide evaluation product queries Address questions/ concerns order availability Accept sales order Inventory configuration TCS2411 Software Engineering

23. Summary • System analysis provides the ‘big’ picture of the computer-based system where software is to be used • By understanding the system, a better software product can be produced • Identification of elements of the system provides the framework for software requirements TCS2411 Software Engineering

24. Software Requirements Specifications • Problem Statement • system reference, problem areas • Data model • Entity Relationship Diagram • Functional requirements • List of functions, Context diagram, DFD • Behaviour model • State Transition Diagram • Glossary of Terms TCS2411 Software Engineering

25. References • “Software Engineering: A Practitioner’s Approach” 5th Ed. by Roger S. Pressman, Mc-Graw-Hill, 2001 • “Software Engineering” by Ian Sommerville, Addison-Wesley, 2001 TCS2411 Software Engineering