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Jackson system development

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Jackson system development (JSD) is a linear software development methodology developed by Michael A. Jackson and John Cameron in the 1980s.

History

JSD was first presented by Michael A. Jackson in 1982, in a paper called "A System Development Method".[1] and in 1983 in System Development.[2] Jackson System Development (JSD) is a method of system development that covers the software life cycle either directly or, by providing a framework into which more specialized techniques can fit. Jackson System Development can start from the stage in a project when there is only a general statement of requirements. However, many projects that have used Jackson System Development actually started slightly later in the life cycle, doing the first steps largely from existing documents rather than directly with the users. The later steps of JSD produce the code of the final system. Jackson’s first method, Jackson Structured Programming (JSP), is used to produce the final code. The output of the earlier steps of JSD are a set of program design problems, the design of which is the subject matter of JSP. Maintenance is also addressed by reworking whichever of the earlier steps are appropriate.

JSD continued to evolve, and a few new features were introduced into the method. These are described in a 1989 collection of papers by John Cameron, JSP and JSD,[3] and in the 1992 version (version 2) of the LBMS JSD manual.[4]

Development of the JSD method came to an end in the early 1990s as Jackson's thinking evolved into the Problem Frames Approach with the publication of Software Requirements and Specifications (1995) and Problem Frames: Analyzing and Structuring Software Development Problems (2000).

Three basic principles of operation of JSD is that:

  • Development must start with describing and modelling the real world, rather than specifying or structuring the function performed by the system. A system made using JSD method performs the simulation of the real world before any direct attention is paid to function or purpose of the system.
  • An adequate model of a time-ordered world must itself be time-ordered. Main aim is to map progress in the real world on progress in the system that models it.
  • The way of implementing the system is based on transformation of specification into efficient set of processes. These processes should be designed in such a manner that it would be possible to run them on available software and hardware.

JSD steps

When it was originally presented by Jackson in 1982,[5] the method consisted of six steps:

  1. Entity/action step
  2. Initial model step
  3. Interactive function step
  4. Information function step
  5. System timing step
  6. System implementation step

Later, some steps were combined to create a method with only three steps.[6]

  1. Modelling stage (analysis): with the entity/action step and entity structures step.
  2. Network stage (design): with the initial model step, function step, and system timing step.
  3. Implementation stage (realisation): the implementation step.

Sunder C stage

It was found by Vasanth Kumar. In the modeling stage the designer creates a collection of entity structure diagrams and identifies the entities in the system, the actions they perform, the time-ordering of the actions in the life of the entities, and the attributes of the actions and entities. Entity structure diagrams use the diagramming notation of Jackson Structured Programming structure diagrams. Purpose of these diagrams is to create a full description of the aspects of the system and the organisation. Developers have to decide which things are important and which are not. Good communication between developers and users of the new system is very important.

This stage is the combination of the former entity/action step and the entity structures step.

Network stage

In the network stage a model of the system as a whole is developed and represented as a system specification diagram (SSD) (also known as a network diagram). Network diagrams show processes (rectangles) and how they communicate with each other, either via state vector connections (diamonds) or via datastream connections (circles). In this stage is the functionality of the system defined. Each entity becomes a process or program in the network diagram. External programs are later added to the network diagrams. The purpose of these programs is to process input, calculate output and to keep the entity processes up-to-date. The whole system is described with these network diagrams and are completed with descriptions about the data and connections between the processes and programs.

The initial model step specifies a simulation of the real world. The function step adds to this simulation the further executable operations and processes needed to produce output of the system. System timing step provides synchronisation among processes, introduces constraints. This stage is the combination of the former ‘Initial model’ step, the ‘function’ step and the ‘system timing’ step.

See also

References

  1. ^ "A System development method" by M. A. Jackson, published in Tools and notions for program construction: An advanced course, Cambridge University Press, 1982
  2. ^ System Development, M. A. Jackson, Prentice Hall, 1983
  3. ^ JSP and JSD: The Jackson Approach to Software Development, ed. John R. Cameron (IEEE Computer Society Press, ISBN 0-8186-8858-0, 1989)
  4. ^ LBMS Jackson system development, Version 2.0 Method manual by LBMS (Learmonth, Burchett Management Systems), John Wiley & Sons, ISBN 0-471-93565-4; 1992
  5. ^ "A System development method" by M. A. Jackson, published in Tools and notions for program construction: An advanced course, Cambridge University Press, 1982
  6. ^ Decision systems Inc. (2002), Jackson System Development. Accessed 24 Nov 2008.

Further reading

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