Info1409 De Montfort University1 Requirements Modelling Systems Analysis & Design Academic Year 2008/9 Info 1409 Lecture 7.
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info1409 De Montfort University1 Requirements Modelling Systems Analysis & Design Academic Year 2008/9 Info 1409 Lecture 7
info1409 De Montfort University2 Lecture Objectives The aims of this lecture are to define: Systems analysis phase activities The need for user involvement in requirements modelling Joint Application development and Rapid Application Development. The Traditional approach Object Oriented approach
info1409 De Montfort University3 Systems Analysis Activities The systems analysis phase includes three main activities (illustrated on the next slide) Requirements modelling Data and process modelling Consideration of development strategies
info1409 De Montfort University4 (1) Systems Analysis Phase 1 – Requirements modeling Requirements modelling begins the process
info1409 De Montfort University5 Requirements modeling To describe and identify the requirements of a new system we need to first gather the facts: required inputs/required outputs Processes Performance Security
info1409 De Montfort University6 Definitions: Outputs refer to electronic or printed information produced by the system Inputs refers to the necessary data that enters the system – either manually or in an automated manner Processes refer to the logical rules that are applied to transform the data
info1409 De Montfort University7 Definitions continued Performance refers to system characteristics such as speed, volume, capacity, availability and reliability Security refers to hardware, software and procedural controls that safeguard and protect a system and its data from both internal and external threats.
info1409 De Montfort University8 (2) Data and Process modeling Once the requirements are modelled then attention moves to modelling the data and processes Diagram from Shelley et al
info1409 De Montfort University9 Data and Process modelling Data and process modeling continues the modeling process by representing graphically (or conceptually) data and processes. There are various methods for doing this, which we will learn about in later lectures and through practical case studies. Examples include Use case models, data flow diagrams, etc.
info1409 De Montfort University10 (3)Development Strategies This phase is concerned with software trends, acquisition and development alternatives for the new system Diagram from Shelley et al
info1409 De Montfort University11 Development strategies “The development strategies phase, considers various development options and prepares for the transition to the Systems Design Phase of the SDLC” (paraphrased from Shelley et al p92) Recap-the systems development life cycle was explained in Lecture 2
info1409 De Montfort University12 Defining the ‘Deliverable’ System Requirements Document This is an overall design for the new system Project management is now needed to co-ordinate people, tasks, timetables and budgets.
info1409 De Montfort University13 Project Management explained The system requirements document provides the ‘blueprint’ of what is needed for the new system. The Project management team then decide upon the best methods to achieve these requirements. There are a number of Methodologies from which to choose.
info1409 De Montfort University14 Methodologies (and Options ) Also called Development strategies During project planning, it is necessary to choose from a range of methods Each methodology (development strategy) uses different techniques to achieve the objectives of the new system requirements.
info1409 De Montfort University15 Activity time Working in 3’s, you will be an A, B or a C: Consider the 3 stages we have just examined: 1. Requirements modelling – A students 2. Data and Process modelling – B students 3. Development strategies – C students
info1409 De Montfort University16 Activity time Working in 3’s, you will be an A, B or a C: Write one or two sentences to explain what your stage is and what the analyst needs to do at that stage.
info1409 De Montfort University17 Feedback and closure Now exchange your notes so that you all have 3 definitions (one for each stage) This is also your opportunity to ask any questions or make any comments. Please be brief – time is short.
info1409 De Montfort University18 Methodology 1) Structured Analysis Often called the ‘Traditional method’ and used extensively in the early days of IT development. Known as Structured Systems Analysis and Design Methodology (SSADM) This methodology treats processes and data as separate entities. Techniques used include Data flow diagrams
info1409 De Montfort University19 Alternatives to ‘Traditional’ “ IT professionals now recognise that successful systems must be USER ORIENTED Users need to be involved formally or informally at every stage of the system development
info1409 De Montfort University20 Result: Team Oriented methods and techniques “ Top managers expect the IT Department to deliver the best possible information system at the lowest possible cost in the shortest possible time” (p93 Shelley et al) To fulfill these expectations many IT managers have tried to increase user participation
info1409 De Montfort University21 (2) Joint Application Development Joint application development (JAD) is a popular fact finding technique that brings users into the development process as active participants. P93 Shelley et al Users have a vital stake in the information system and so should participate fully in the development process
info1409 De Montfort University22 The JAD approach The JAD approach is a team approach which involves a task force of users, managers and IT professionals. They work together to: Gather information Discuss business needs Define the new system requirements
info1409 De Montfort University23 Typical JAD session Agenda
info1409 De Montfort University24 (3) Rapid Application Development Characteristics RAD is another team based technique. It speeds up the information system development process It produces not just the model (as in JAD) but a fully functioning new information system quickly. RAD is a complete methodology with a 4 phase life cycle.
info1409 De Montfort University25 The four phases of the RAD model Notice the continuous interaction between user design and construction
info1409 De Montfort University26 (4) Object Oriented Methodology Object oriented analysis or O.O. combines data and the processes that act on the data into things called objects. These objects represent things, transactions and events that affect the system
info1409 De Montfort University27 Object Oriented methods This module will introduce and explain O.O methodology. Lecture 8 will focus on how CASE tools and Unified Modelling language can be part of Object Oriented analysis concepts.
info1409 De Montfort University28 In conclusion This lecture has given you the opportunity to: Examine systems analysis phase activities recognise the need for different development strategies (methodologies) Be introduced to Traditional methods, OO, Joint Application development (JAD) and rapid application development (RAD) Understand the need for User involvement in the requirements modeling process.