Systems Analysis And Design

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Systems Analysis And Design

• CASE Tools

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What is CASE

• Computer Aided Software Engineering
• A piece of software that assists in the
  development of a system
• Bottom end
• Compilers, debuggers, drawing package
• Top end
• Integrated programs that guide developer through
  process of building and managing a system
• Not a methodology, but based on one
• Notation
• Procedure
• Documentation

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What CASE Tools can do

• Automate Modelling techniques!
• Draw a context diagram, and then explode this to
  level 1 and level 2
• CASE tool will check work is consistent with any
  previous diagrams
• Show all relevant inputs and outputs
• Check between ERM and DFDs

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Why did it appear?

• Demand
• Timescales
• Quality
• Software Quality/Reliability
• errors at the specification stage can be
  difficult to detect and expensive to correct
• need a precise and consistent definition
• Software development needs
• planning
• co-ordination
• configuration management
• quality assurance

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The Background

• Existing strategies
• classic approaches
• separate departmental strategies
• packages
• prototyping
• CASE supports the adoption and application of a
  methodology for SA D
• Provides
• assistance
• rigour

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Hows it help?

• Live diagram
• Can help with prototyping
• Can help with seeing what happens when user
  suggests something
• No need to re-draw diagram
• Can make neat, easy hard copies
• Can move things around the screen

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History

• 1st Generation (late 70's) - Code generators,
  Simple diagrammers, 4GLs, DBMS
• 2nd generation (mid 80's) - Data Dictionary,
  RDBMS, 4GEs, Multi diagrammers
• 3rd Generation (late 80's) - Intelligent
  diagrammers, DB generators, Active Data
  Dictionaries
• 4th Generation (90's) - Method/technique support,
  Application Generators, Simulation and capacity
  planning, Project management, Reverse
  Engineering, Methods Engineering

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Terms

• CASE
• Workbench
• Repository
• Upper Case
• Lower Case
• Integrated Case
• Re-engineering
• Reverse Engineering
• IPSE

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Case

• CASE tool is usually a highly sophisticated
  collection of software
• Help in all areas especially
• Diagrams
• Cross Checking
• Documentation
• Automate the whole process from initial
  identification of customer requirements to
  automatic code generation
• Several CASE tools may be necessary in one project

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Workbench

• Includes all tools for a particular task
• Analysis Workbench offers tools for DFDs, ERMs,
  process definitions labelling, reports on models
  produced.
• All tools in a particular workbench are
  integrated and work together
• There is also integration between different
  workbenches in the same CASE tool

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Repository

• Encyclopaedia or dictionary
• Core of any CASE tool
• Holds all information
• Enables cross referencing between diagrams,
  models and workbenches
• Reflects changes in the developing system

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Upper CASE

• Tools which support the analysis and design of
  software systems
• Produces analysis reports
• Modelling of organisations functional
  requirements
• Assist analysts and users in drawing boundaries
  for project
• Visualise how the project meshes with the other
  parts of the organisation
• Some support prototyping of screen and report
  design

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Lower CASE

• Tools which support programming and testing
• Generates computer source code
• Generates in more then one language

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Integrated Case

• Full coverage of life cycle
• Tools fully integrated any tool can employ info
  from another - they share the same repository.
• Repository checked automatically ( to ensure
  integrity, consistency and completeness)
• Generators for Screens, Reports, Programs, Menus
• Self documenting, robust, interactive and
  dynamic.
• Producing bridges with other supplier's tools to
  enable some flexibility of use

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CASE Life Cycle
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Re-engineering

• Restructure inefficient or badly constructed code
  using a CASE tool
• A way of restoring legacy systems

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Reverse Engineering

• When documentation is so sparse or confused that
  is is impossible to work out what the program was
  supposed to do
• Feed the old piece of software into a CASE tool
  to find its original purpose

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IPSE

• Integrated Project Support Environment
• CASE tools for the management of the system
  development project.
• Offer Project Management Tools
• Schedule Planning
• Cost Estimating
• Version Control
• Time Accounting
• Problem Recording

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Tools with a CASE system

• Diagramming Tools
• Description Tools
• Prototyping Tools
• Enquiry and reporting tools
• Quality Management Tools
• Decision Support Tools
• Document Organisation Tools

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Tools with a CASE system

• Design Generation Tools
• Code Generator Tools
• Application Generator Tools
• Testing Tools
• Data Sharing Tools
• Version Control Tools
• Housekeeping Tools

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Advantages Of CASE Tools

• Tools based on structured Techniques
• Faster, More efficient than by hand
• Cross Checks
• Fast, accurate detection of errors, omissions and
  inconsistencies
• Diagrams altered with ease

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Advantages of CASE (Cont)

• Increasing Productivity
• Improved Quality
• Improved communication with customer
• Rapid Development
• Consistent documentation
• Developer has more time to concentrate on
  creative side of the work

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Disadvantages Of CASE

• Very expensive
• Tied to a particular methodology
• Means commitment to that methodology - changing
  working practices
• Training
• CASE does not replace a poor developer
• Customisation - Lack of facilities
• Complete support?

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Will CASE help Develop More Reliable Software?

• Projects need to have a clearly defined scope and
  limited objectives
• Plan realistically
• provide training in methods and tools
• review revise working procedures
• define configuration procedures
• CASE is a good servant but a bad master
• Tools are never a substitute for thinking
• BUT can provide much needed automated support,
  leaving the developer to focus on the quality of
  the deliverables

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CASE Selection

• Selection criteria needs to be defined
• Training
• techniques of underlying methodology
• supporting tool set
• Standards
• Methodology
• integration of existing standards / procedures /
  systems
• QA and review procedures
• Model Management
• Data and functional models need to be managed
• change control procedures

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Examples Of CASE Tools

• SELECT SSADM
• Visible Analyst (Visible Systems Corp)
• Magec (AI Lee)
• Foundation (Anderson Consulting)
• Teamwork (Cadre Technologies)
• PacBASE (CGI Systems Inc)
• LBMS Systems Engineer
• BIS IPSE
• And lots more.

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The Future

• Web enabled technology
• Java
• Expert systems
• Object Orientation

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SELECT SSADM

• Drawing of DFDs , ERMs
• Data Dictionary
• Inbuilt checking facility
• Automatic downwards update
• Check syntax of diagrams

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SELECT Hints

• Save your project somewhere logical!
• If Parent is Context diagram then child is level
  one DFD. Child of each process at level one is
  level 2 DFD
• Use check feature when you have built the diagram
• Dont leave too many external entities on there