System Engineering and Analysis. system environments. Lecture Objectives. System Elements. Definition of System. Information system types

Transcription

1 System Engineering and Analysis What is the role of the software? Information system types Manual (read a text by your eyes then summarize using your pen) Automated (get the rmation through a computerized system) Data Process Information TCS2411 Software Engineering 1 TCS2411 Software Engineering 4 Lecture Objectives To examine the elements of a computerbased system To understand the development process of a system To illustrate the representations of a business rmation system system environments Internal, like users, organization structure and procedures External, consists of all factors outside the organization that affect the system TCS2411 Software Engineering 2 TCS2411 Software Engineering 5 Definition of System A collection of interrelated components that work together to achieve some objective Objective: to develop a, to support business functions etc. TCS2411 Software Engineering 3 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 rmation that is accessed via the software. Documentation: descriptive rmation 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 6 1

2 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 7 TCS2411 Software Engineering 10 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. 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 8 TCS2411 Software Engineering 11 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 rmation users need to perform their job Maintenance, Review and Test Amendments (fix) by the programmers System audit, by the programmers and analyst TCS2411 Software Engineering 9 TCS2411 Software Engineering 12 2

3 System Engineering Hierarchy Exogenous & Endogenous Inputs Domain of interest System element Business or domain World view Domain view Element view 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 Detailed view TCS2411 Software Engineering 13 TCS2411 Software Engineering 16 System Engineering Hierarchy continue Restraining Factors of System Model 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. Assumptions Simplifications Limitations Constraints Preferences TCS2411 Software Engineering 14 TCS2411 Software Engineering 17 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 Enterprise Modeling Organizational structure Business-level data modeling Process modeling Information flow modeling TCS2411 Software Engineering 15 TCS2411 Software Engineering 18 3

4 Corporate Support Finance Organizational Structure Sales & Marketing Planning XYZ Company Engineering.. Manufacturing TCS2411 Software Engineering 19 Contact record Establish customer contact Product description evaluation Information Flow Modeling Product queries Address questions/ concerns Customer Check Prepare delivery d.o. Accept sales Inventory configuration TCS2411 Software Engineering 22 Business-level Data Modeling Summary Product A purchases evaluates inquires about describes sells Customer Salesperson contacts assists System analysis provides the big picture of the computer-based system where software is to be used By understanding the system, a better software can be produced Identification of elements of the system provides the framework for software requirements TCS2411 Software Engineering 20 TCS2411 Software Engineering 23 Process Modeling Establish customer contact evaluation Address questions/ concerns Accept sales Check Prepare delivery TCS2411 Software Engineering 21 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 24 4

5 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 25 5