The CommonKADS Design Model - PowerPoint PPT Presentation

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The CommonKADS Design Model

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represent the expert knowledge and design specification in form of text or diagrams ... Worked Example I: IMPRESS. Diagnose faults in machine ... – PowerPoint PPT presentation

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Title: The CommonKADS Design Model


1
The CommonKADS Design Model
  • Introduction to CommonKADS
  • CommonKADS Design Model
  • Worked Example
  • Conclusion

2
Introduction to CommonKADS
  • Problem faced by Knowledge Engineers
  • --designing good KBS relies on knowledge
    engineer abilities
  • Approach to the problem--CommonKADS
  • --represent the expert knowledge and design
    specification in form of text or diagrams
  • Important components of CommonKADS
  • --Expertise Model domain knowledge,inference
    knowledge, task knowledge
  • --Design Model

3
The CommonKADS Design Model
  • Intends to support knowledge engineers in
    choosing knowledge representations and
    programming techniques
  • Three-stage transformation process
  • --Application design
  • --Architectural design
  • --Platform design

4
Application Design
  • Purpose is to decompose the knowledge into
    manageable chunks
  • Three approaches
  • --Functional decomposition
  • --Object-oriented decomposition
  • --AI paradigms

5
Functional Decomposition
  • Treat each inference step from the Expertise
    Model as a chunk of functionality
  • Benefits
  • --replicate expert problem solving process
  • --canonical inference has its expected
    functionality already defined
  • --preserve task structure

6
Object-oriented Decomposition
  • Treat each concept from the domain model as a
    chunk of data--an object class
  • Preserve the structure of the domain models in
    the expertise model
  • inference and task structure may be maintained
  • Have difficulty in assigning production rules
    because they refer to more than one objects

7
AI Paradigm
  • Include blackboard system, constraint-based
    programming, qualitative simulation, or
    model-based reasoning
  • chunkof knowledge may be constraints, knowledge
    sources, or whatever appropriate for the chosen
    approach
  • little of the structure of the expertise model
    will be maintained

8
Architectural command
  • Characterize the contents of each chunkafter
    decomposition to specify further design
    requirements
  • A function name that describe the action which
    the function performs
  • --e.g. an inference step of type select-subset
    can be implemented by a subset command
  • Help validate the Expertise Model

9
Architectural Design
  • Task is to define a computational infrastructure
    capable of implementing the architecture commands
    defined in the application design
  • Emphasis is on choosing ideal techniques
  • Experience of knowledge engineer can play an
    important role

10
Platform Design
  • Consider how the ideal knowledge representation
    and inference techniques should be implemented in
    chosen software
  • Knowledge representation is not a problem
  • Some programming techniques may be awkward to
    implement

11
Worked Example I IMPRESS
  • Diagnose faults in machine
  • Application design functional decomposition
  • Architectural design
  • --knowledge representation objects
  • --inference step production rules,
    object-based operations
  • Platform design KAPPA-PC on Compaq 386
  • Flow of control based on task structure from the
    Expertise Model

12
Worked Example II X-MATE
  • Assess the ability of mortgage applicants
  • Application design functional decomposition
  • Architecture design select data source, use
    production rules, choose rule set, use arithmetic
    functions
  • Platform design KAPPA-PC 1.1 on HP Vectra 386 PC
  • Flow of control repeat running through the whole
    inference structure

13
Conclusion
  • CommonKADS provides useful documentation of
    system design process
  • Encourage greater modularity and reusability of
    designs
  • Help to validate the Expertise Model
  • Weakness
  • --lack of guidance on selection of techniques
  • --lack of a defined set of architectural
    commands
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