COMM89 Knowledge-Based Systems Engineering Lecture 8 Life-cycles and Methodologies

Lifecycles and Methodologies Unstructured methodology  prototyping We will be looking at 3 structured methodologies. These are -  Blackboard Architectures  KADS (Knowledge Acquisition Design Strategy)  HYM  Others exist such as POLITE, RUDE and GEMINI

Lifecycles and Methodologies Analysis Design Implementation Validation Installation Maintenance Quality Assurance Project Management Use of Standards Traditional software development life cycle

Lifecycles and Methodologies An incremental prototyping approach for large or complex systems. Design Prototype Implement Prototype Evaluate Identify Requirements

Lifecycles and Methodologies Prototyping  iterative  evolutionary  exploratory  many small-medium systems designed this way Advantages of using an incremental prototyping approach -  Allows the accuracy of the knowledge base to be demonstrated during iterations of the lifecycle  system more likely to match users requirements  The quality of the reasoning is open to inspection  It provides an easy mechanism to involve the users, management and experts  It allows the project to be signed off as complete

Lifecycles and Methodologies Disadvantages of using an incremental prototyping approach -  The ability to develop small projects does not always mean that it is possible to develop and maintain large real-world systems  Difficult to define the cost and timetables  can be difficult to track versions  encourages users to ask for more features  may not match QA procedures

Lifecycles and Methodologies Structured methodologies Blackboard Architectures  Similar to a group of experts working around a blackboard  Provide a problem solving model for organising knowledge  Provide a potential strategy for applying the knowledge  Allow a range of knowledge representation methods to be applied  Segment the knowledge base, making it more maintainable and the implementation more efficient

Lifecycles and Methodologies Blackboard Architectures Working Memory IE KB Knowledge Sources Blackboard

Lifecycles and Methodologies HEARSAY II Blackboard Architecture  developed for speech understanding speech understanding is difficult large search space noisy, incomplete data  problem solving is imprecise/incomplete  three components blackboard: shared by all knowledge sources knowledge sources: Control: agenda based

Lifecycles and Methodologies HEARSAY II Blackboard Architecture  Developed at Carnegie Mellon University (1978)

Lifecycles and Methodologies KADS - (Knowledge Acquisition Design Strategy) KADS developed 1990, KADS II (common KADS 1994) Concerned with modeling problem domain. Objectives of KADS Structured activities for:  Analysis (stages)  Design (stages) Definitions of deliverables (templates/framework) Advice and guidance on techniques to use Advice and guidance on the tools Support for Quality Assessment and Control (QAC) Identified opportunities for prototyping

Lifecycles and Methodologies KADS - (Knowledge Acquisition Design Strategy) Common KADS Analysis (stages)  Process analysis  Cooperation analysis  Expertise analysis  Constraint analysis  Systems analysis Design (stages)  Global design  Knowledge based system design

Lifecycles and Methodologies KADS - (Knowledge Acquisition Design Strategy) Why use KADS  structuring KBS development  separates technical from management activities  maintenance  standard approach for KBS development  multiple experts  encourages reusable components

Lifecycles and Methodologies KADS - (Knowledge Acquisition Design Strategy) supports the development of various models including - The process or organisational model The expertise model MIKE (Model based Incremental Knowledge Engineering) Protégé II

Lifecycles and Methodologies HYM supports the creation of hybrid information systems  It aims to provide an enhanced software development lifecycle that supports project development both incrementally and in one go  It has a combined analysis and design phase that supports a smooth transition between the two  The combined phase is highly iterative, and contains detailed design evaluation and quality assurance procedures  It supports the seamless integration of KBS components with traditional IS components  Supports integration of a number of methods to overcome the limitations of each

Lifecycles and Methodologies Hybrid information system Hybrid information system level Components level Repositories level Procedures Databases Knowledge Traditional system Hybrid system KBS The HYM 3 layer architecture

Lifecycles and Methodologies Factors for and against structured methodologies  For structured documented well-understood tried and tested may have tool support visible for project management/control QA may be built in  Against need to learn them may be unwieldy may not be applied to all situations take time to apply necessity for documentation