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Further Systems Analysis

Further Systems Analysis. Plan. Introduction Structured Methods Data Flow Modelling Data Modelling Relational Data Analysis Further Data Modelling Further Systems Analysis Topics. Information and Systems. …and Information Systems. Systems.

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Further Systems Analysis

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  1. Further Systems Analysis

  2. Plan • Introduction • Structured Methods • Data Flow Modelling • Data Modelling • Relational Data Analysis • Further Data Modelling • Further Systems Analysis Topics

  3. Information and Systems …and Information Systems

  4. Systems • There is no universally accepted definition of a system • Properties that are generally considered part of a good definition • An organised or complex whole • An entity that consists of independent parts • These parts are affected by being part of the system and are changed by being removed from the system • A collection of related activities working together to achieve a common objective • An assembly of parts that have been identified by an individual as being of special interest

  5. Boundary Systems A system is defined by its boundary Environment System The system boundary sets it apart from its environment

  6. Systems Different observers will view a system in a different way There may be a different physical context – e.g. CD Hotels

  7. Systems Different observers will view a system in a different way It may be that the difference is more conceptual It’s the same system but it is described using a different set of symbols

  8. Systems Different observers will view a system in a different way Both of these situations can cause problems for the systems analyst

  9. Systems A system will consume resources from its environment Environment System A system will also produce some output These may be physical or conceptual

  10. Biological Systems • Frogs • Inputs • Outputs Natural Systems – Goal unclear

  11. Inputs Physical Resources People Information Money Outputs Physical Goods People Information Money Man Made Systems There will usually be some transformation There will be a Goal We are interested in information

  12. Systems The environment may be static Environment System Magnitude and rate of change are important Or it may be dynamic

  13. Systems A system must be able to change to match its environment Environment System System Change – By reconfiguration of components/resources Change – To achieve its goal

  14. Impact on Development • We must be aware of the system’s environment • Static/Dynamic • Rate of change • The system must be able to • React to change • Reduce the effect of change

  15. Law of Requisite Variety • A system must be as complex as the environment in which it operates • Therefore it must be able to reconfigure it’s resources to react to environmental changes

  16. Practical Solutions Redesign the system System System System Create Adaptive Systems Add new components to the system

  17. Information Definitions • ‘Information is data which has been processed in such a way that it has meaning to the person who receives it, who may then use it to improve the quality of decision making.’ CIMA Information Management Study Text • ‘‘Information’ refers to the aggregation of data that - when it is interpreted and understood - provides systems users with knowledge of some kind.’ Edwards et al., The Essence of Information Systems • ‘Information is raw data converted into a form to enable the user to make a decision in response to a business need.’ Thomas and Ballard, Business Information • ‘Information is data that have been processed in such a way as to be useful to the recipient.’ Rowley, Strategic Management Information Systems and Techniques

  18. Information • Structure • Data is brought together to have some meaning • Processing • The data must be processed to give it structure • Communication • Information should communicate something to the recipient

  19. Information - Structure • See TopDog examples

  20. Information - Process • In order to become information, data must undergo some form of Transformation, Processing or Formatting • ‘One person’s data is another person’s information’ McCleod, 1998

  21. Communication • General Communications Channel

  22. Information • Structure • Processing • Communication • Similar properties to systems • In order for information to exist there must be a system to produce it • We control information by systems development

  23. Review of SAD

  24. The Problem of Development • Development views of the system • System development is complex problem • We handle complexity by dividing the problem • Process View • Data View • Dynamic View

  25. Information System Architecture 2 5 1 6 4 7 3

  26. 1. Users • Users send commands and instructions across the user interface • Users send and receive data across the user interface • The interface will also implement security controls (e.g. log in passwords etc)

  27. 2. User Interface • How do we present information to our users? • How do we collect data? • UI may be written in languages such as Visual Basic • May even be written in HTML with scripting languages

  28. 3. User Interface • Technology Used – HCI • Usability Issues – Process and data Design • Navigation – State Transition Diagram • Design – GUIIN real systems People and Paper also form part of this interface (e.g. phone banking)

  29. 4. Processes • The business processes are described using DFDs and other models (ELH, STD). • They will be implemented in a programming language such as Visual Basic, Java, C++ • Should keep their implementation separate from the GUI

  30. 5. Data Interface • There is an interface between the business processes and the data • This is often implemented using SQL (structured query language) • If a file system other than an RDB is used then this interface must be implemented by some other means.

  31. 6. Database • The database is defined in the data model • Described in the process model • via data dictionary • Usually implemented in a Relational database • Oracle, Access, MySQL • May also be implemented as paper files or electronic files (e.g. HTML)

  32. 7. System Boundary • Defines the scope/context of the system • Identified in the DocFD and Context Diagrams • All access to the system should be via the user interface • Some users may be other systems • All interfaces need to be carefully defined to avoid security, and other problems

  33. Development Process • What is the scope/context of the system? • What must it do? What are its outputs? • Requirements Gathering – Rich Pictures/DFDs • What Processes are needed to do it? • What data do the processes require? • Requirements Analysis – DFDs/ERDs

  34. Development Process • How do we store the data (relational DB)? • Database Design - Normalisation • How will the users use the system? • Interface Design – State/Transition Diagrams

  35. Information System Architecture 2 5 1 6 4 7 3 It is clear that we cannot develop any part of the system in isolation

  36. Structured Methods We therefore need to introduce a certain amount of iteration into our development process

  37. The End • Have a good one…

  38. References • Whiteley, D. (2004) Introduction to Information Systems, Palgrave, 2004. • Lejk, M. and D. Deeks (2002) Systems Analysis Techniques, Addison Wesley 2002 • Mason, D. and L. Willcocks (1994), Systems Analysis, Systems Design, Alfred Waller, 1994.

  39. References • Yeates, D. and T. Wakefield (2004) Systems Analysis and Design, FT/Prentice Hall 2004 • Gane, C. and T. Sarson (1979) Structured Systems Analysis, Prentice Hall, 1979 • Eva, M (1994) SSADM Version 4: A users guide, McGraw hill, 1994

  40. References • DeMarco, T. (1979) Structured Analysis and System Specification, Yourdon, 1979 • Royce, W. (1970) Managing the development of large software systems, In: Proceedings of IEEE WESCON, 1970 pp1-9. • Connolly, T. and C. Begg (2000) Database Solutions, Addison-Wesley, 2000

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