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Lecture 13 Revision IMS9001 - Systems Analysis and Design.

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Presentation on theme: "Lecture 13 Revision IMS9001 - Systems Analysis and Design."— Presentation transcript:

1 Lecture 13 Revision IMS9001 - Systems Analysis and Design

2 13.2  System concepts and information systems  The Systems Development Life Cycle (SDLC)  The analysis and design phases of the systems development life cycle:  Systems analysis issues and techniques: information gathering process modelling data modelling Revision

3 13.3 Revision  Design and implementation issues and techniques: generating and evaluating design alternatives system architecture; finalising design specifications interface design implementation - testing, conversion, acceptance planning, documentation maintenance  General systems development issues communication and documentation quality issues overview of project management types of information systems

4 13.4 Information systems  An Information System is a formal arrangement of people, data, processes integrated to help manage complexity and to support and improve business operations, as well as supporting the problem-solving and decision-making activities of managers.  It transforms Data into Information

5 13.5 Systems development and the SDLC  The need to build new information systems or change existing ones comes about because:  there are problems in the way in which existing systems operate; or  changes in circumstances create opportunities to improve things by doing them differently; or  there are external requirements or pressures, e.g. new government legislation

6 13.6 The Systems Development Life Cycle The SDLC provides:  a systematic and orderly approach to solving business problems  a means of managing, directing, monitoring and controlling the process of system building, including:  a description of the process - steps to be followed  deliverables - reports/programs/documentation/etc  milestones - dates of completion of steps or deliverables

7 13.7 Systems Development Phases Analysis Design Implementation Review Maintenance Quality Documentation Ethics Project Management Analysts Role Initiation

8 13.8 Systems Development Activities involved in building computer- based information systems are:-  identifying problems  analysing and describing information and processing needs  designing solutions to meet those needs  acquiring/building new systems  implementing new systems  maintaining information systems

9 13.9 Data Gathering The data gathered should include:  system description - how things work or should work  system problems - what is wrong or needs improvement  opportunities - identifying scope for innovation or new ways of doing things  what is technically possible  what constraints exist

10 13.10 Data gathering techniques  Interviews  Questionnaires  Observation  Reports  System Documentation

11 13.11 Modelling  Why do we do it?  Communication with ourselves  Communication with others  How do we do it?  informal techniques  formal techniques  How effective is it?  different techniques for different purposes  eg. a road map, an organisation chart, a data flow diagram

12 13.12 Modelling perspectives Data Process Behaviour The Organisation

13 13.13 Process modelling  processes are the “action” part of businesses  process modelling graphically represents the processes which act on data to  capture  manipulate  store  distribute

14 13.14 Process modelling  principal techniques  functional decomposition  data flow diagrams  associated techniques for modelling the details of low-level processes  structured English  decision tables and decision trees

15 13.15 Data flow diagrams (DFDs)  model the flow of data into, through, and out of an information system  represent an information system as a network of communicating processes  show the processes that change or transform data  show the movement of data between processes

16 13.16 Logical and Physical DFDs Physical DFDs Logical DFDs View How processing is What the system does implemented Processes Actual sequence Essential sequence Naming Forms, locations, Underlying data and people/roles activities Data flows Excess/duplicated data Only essential inputs for implementation and outputs of the needs processes

17 13.17  data “objects” are things about which we wish to store information  ER models show the major data objects and the associations between them  ER models are useful in the initiation, analysis and design phases Entity relationship modelling

18 13.18 Human–Computer Interface Design INTERFACEINTERFACE INTERFACEINTERFACE Programs Database end user direct user The interface is the link between the users and the computer To many users the interface is the system

19 13.19 The Basics of Interface Design Five Principles or “Commandments”:  Support “Transportability of Knowledge”  Be Consistent  Provide Feedback  Use Drab Colours  Make the User Boss

20 13.20  implementation planning  Build and test software  Build/modify databases, networks etc.  finalise documentation  prepare the site  convert data into required form and media  conduct training  install system  monitor system  transition to maintenance mode  post-implementation review Implementing the System

21 13.21 Stages of Testing Performance test Function test Unit (module) test Installation test Acceptance test Integration test tested modules integrated modules functioning system validated software accepted system system in use

22 13.22 Install the System ALTERNATIVES: Direct installation or Abrupt cut-over; Parallel installation; Phased installation or Staged installation; Pilot installation or Single Location conversion.

23 13.23 Maintenance  Corrective - fix errors  Adaptive - satisfy changing needs  Perfective - enhance performance  Preventative - fix potential problems  If the cost of maintenance is too high consider other options:  new development, purchase a software package, re-engineer/modify

24 13.24 Documentation  Not necessarily a piece of paper.  Any permanent medium used to communicate to other people can be classed as documentation  Product and documentation should be developed at the same time  DOCUMENTATION IS PART OF THE PRODUCT Documentation is communication:  the objective is to:  create a specific effect  on particular readers  who want specific information,  have particular characteristics and  will read under particular circumstances.

25 13.25  the data dictionary is a database or repository of information about objects identified during systems development  every object (and each of its components) must have a definition in the data dictionary  the data dictionary is a major source of documentation about the information system Data Dictionary

26 13.26 Project management: why is it needed?  the number of people involved  the number of tasks to be done  the extent of the interaction between the tasks and people  the complexity of the interactions between the tasks and people

27 13.27 Basic process of project management  Select systems development methodology  Plan the project tasks  Estimate the resources and time required to complete individual phases of the project  Staff the project team  Organise and schedule the project effort(tasks/time/ people/technical resources) and therefore cost  Control the project development (directing the team, controlling progress, replan, restaff,.... )

28 13.28 Quality in systems development  various definitions e.g. Ability to satisfy stated/implied needs  the cost of detecting and correcting errors rises greatly during the SDLC  must be embedded in the systems development process: product and process  implementing quality: e.g. standards, technical reviews

29 13.29 Types of Information Systems  There is a range of information systems to serve the varied needs of users:  Transaction processing systems  Electronic commerce  Process control systems  Management support systems: Management information systems, Decision support systems, Executive information systems  Knowledge-based systems: Expert systems, Neural networks, Robotics  Multimedia systems  Office automation systems  Geographical information systems

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