CSI315 Web Applications and Technology Overview of Systems Development (342)

Definitions A System: A purposeful collection of interrelated components working together towards a common objective. A system may include software, mechanical, electrical and electronic hardware and the people who perform the operations. Information System Assumed to mean computer-based information systems, which are combinations of hardware, software, and telecommunications networks that people build and use to collect, create, and distribute useful data.

Definitions Software System Written programs or procedures or rules and associated documentation pertaining to the operation of a computer system Application software is a subclass of computer software that employs the capabilities of a computer directly to a task that the user wishes to perform.

Systems Analysis and Design –Complex process whereby computer- based information systems are developed and maintained Application Software –Result of systems analysis and design –Designed to support specific organizational functions or processes

System Development Life Cycle Provides a series of predictable series of phases for system development. –Phases are not necessarily sequential –Each phase has a specific outcome and a deliverable –Individual companies use customized life cycles Every system, small or large, passes through the stages of the SDLC

System Development Life Cycle Problem recognition Feasibility Study Analysis Design Construction and Implementation Maintenance

Problem Recognition Prepare statement specifying scope and objective of the problem What is the problem being addressed? Is it an introduction or a change/improvement? What are the the business needs to be provided?

Feasibility Study A test of the systems proposal according to its workability, impact on the organization, ability to meet user’s needs and effective use of resources. The Analyst studies the problem to assess its magnitude The Analyst Lists what is wrong with the current system/situation Determines if the needed system is technically, humanly and economically feasible for the environment The result is a formal report of what is to be done if given the

Analysis A detailed study of the various operations performed by the system and their relationships within and outside of the system Studying the current system ( documents, procedures, programs, design charts, glossaries of errors) Defining the requirements of the new system (fact gathering, DFD’s, system flowcharts, data models, process specification) Compile problem specification detailing the old system and what the new system is expected to do.

Design Technical specifications that will be applied in implementing the system. Design the I/O, processing and file design (DFD’s, System Flow Charts, I/O design forms/formats, data models, process specification) The functional diagrams of the analysis phase translated into the plans for a series of computer programs which will perform the required functions The design specification contains all the information that the programmer will need.

Construction The computer environment is prepared, the programs for the new system written, tested and documented The analyst plans and supervises the writing, testing and correction of programmers Programmers write new programs or modify purchased ones Analysis plans the testing procedures User verifies the subsystem Analyst supervises the installation and documentation

Maintenance System modification made after the system is operational Recognize the problem Prepare incremental model Modify programs and documentation if needed Test the new system

System Analysis and Design Methodologies(342) SSADM Object-Oriented and Analysis and Design Prototyping Soft System Methodology

Software Computer programs and associated documentation Software products may be developed for a particular customer or may be developed for a general market Software products may be –Generic - developed to be sold to a range of different customers –Bespoke (custom) - developed for a single customer according to their specification

What is software engineering? Software engineering is an engineering discipline which is concerned with all aspects of software production Software engineers should –adopt a systematic and organised approach to their work –use appropriate tools and techniques depending on the problem to be solved, the development constraints and the resources available

What is the difference between software engineering and system engineering? Software engineering is part of System engineering System engineering is concerned with all aspects of computer-based systems development including »hardware, »software and »process engineering System engineers are involved in system specification, architectural design, integration and deployment

What is a software process? A set of activities whose goal is the development or evolution of software Generic activities in all software processes are: –Specification - what the system should do and its development constraints –Development - production of the software system –Validation - checking that the software is what the customer wants –Evolution - changing the software in response to changing demands

Software Process Model A simplified representation of a software process presented in a specific view Examples of software process models/paradigms WaterFall Model (classic and oldest) Evolutionary development-prototyping Formal Transformation Intergration from re-usable components

Applications An application is a software executable designed to perform a specific function. –Adobe Photoshop is an example of an application designed to perform image editing. –Microsoft Word is an example of an application designed to perform word-processing.

Web Applications A web application is an application delivered to users from a web server over a network such as the World Wide Web or an intranet. A Web application uses a web site as the front-end to a more typical application. In a web application client data input executes business logic on the server.