Task Specific Knowledge Based Task Specific Knowledge Based Systems - PowerPoint PPT Presentation

Task Specific Knowledge Based Task Specific Knowledge Based Systems and Their Application Systems and Their Application Ahmed Kamel Ahmed Kamel North Dakota State University North Dakota State University

Outline Outline First Generation Expert Systems First Generation Expert Systems � � Task Specific Architectures Task Specific Architectures � � Generic Task Approach: Generic Task Approach: � � – Structured Matching – Structured Matching – Hierarchical Classification – Hierarchical Classification – Routine Design Routine Design – – Functional Modeling Functional Modeling – Applications: Applications: � � – Engineering Design Engineering Design – – Agricultural Farm Management Agricultural Farm Management – – Adaptive Traffic Control Adaptive Traffic Control – – Computer Network Security Management – Computer Network Security Management Conclusions Conclusions � � 2

First Generation Expert Systems First Generation Expert Systems � Focus is on representation Focus is on representation � e.g. Rule- -based systems based systems e.g. Rule � All knowledge represented in one form All knowledge represented in one form � e.g. If condition condition then then action action e.g. If � Control is separate from knowledge Control is separate from knowledge � 3

Strengths Strengths � Uniformity of representation Uniformity of representation � � Modularity of knowledge Modularity of knowledge � � Change domains by changing rules Change domains by changing rules � � Rules are easily expressed in English Rules are easily expressed in English � � Rule trace provides explanation Rule trace provides explanation � facility facility 4

Limitations Limitations � No guidance in problem analysis No guidance in problem analysis � � No direct mechanism for expressing control No direct mechanism for expressing control � knowledge knowledge � Problems with scale Problems with scale- -up up � � Very hard to maintain: Very hard to maintain: � rules are not really independent rules are not really independent 5

Lesson from First Generation Lesson from First Generation It is difficult to separate knowledge It is difficult to separate knowledge from its use. from its use. Knowledge Inference Knowledge Inference Base Engine Base Engine 6

Task Specific Architectures Task Specific Architectures A task specific architecture directly directly A task specific architecture supports specification of the supports specification of the knowledge needed to carry out a knowledge needed to carry out a specified mapping of input to output. specified mapping of input to output. Examples of tasks include design, Examples of tasks include design, classification, ... classification, ... 7

Level of Generality Level of Generality task specific task specific specialized general purpose specialized general purpose too specific, too general too specific, too general lose ability for purpose, lose lose ability for purpose, lose reuse of the constraints on reuse of the constraints on approach/shell knowledge and approach/shell knowledge and inference inference middle ground middle ground 8

Task Specific Architectures Task Specific Architectures � Several task Several task- -specific architectures exist to support specific architectures exist to support � the development of knowledge- -based systems based systems the development of knowledge � Different architectures share a common Different architectures share a common � philosophy, however they differ on the level of philosophy, however they differ on the level of granularity of the tasks and on whether or not granularity of the tasks and on whether or not representation and use of knowledge should be representation and use of knowledge should be separate separate � Furthermore, different architectures provide Furthermore, different architectures provide � mechanisms for the representation of knowledge mechanisms for the representation of knowledge or its use or both or its use or both 9

Generic Task Approach Generic Task Approach � Human reasoning is based on a set of generic problem solving types out of which complex reasoning is composed � An attempt is made to identify these problem solving types and to build software to support these types of problem solving � For each identified method, a a representation template and a control regime are provided The embodiment of which amounts to a language tailored for each specific GT that is identified. 10

Characteristics of a GT Characteristics of a GT � Information Processing Task (i.e. Information Processing Task (i.e. � input/output relationship) input/output relationship) � Organization of Knowledge Organization of Knowledge � � Control principles Control principles � e.g. Hierarchical classification, Routine e.g. Hierarchical classification, Routine Design, … …. . Design, 11

Structured Matching Structured Matching � A mechanism for imposing a structure on rules A mechanism for imposing a structure on rules � � Organizes rules into small decision tables Organizes rules into small decision tables � � Each decision table produces a result using some Each decision table produces a result using some � ordered metric: ordered metric: – 0 0 … … 5 5 – – Excellent, very good, good, neutral, poor Excellent, very good, good, neutral, poor – – strongly match, match, neutral, against, strongly against strongly match, match, neutral, against, strongly against – – etc. etc. – � Decision tables may refer to the results of other Decision tables may refer to the results of other � decision tables decision tables 12

Structured Matching Example Structured Matching Example 13

Hierarchical Classification Hierarchical Classification � Knowledge Organization Knowledge Organization � – hierarchy of specialists of specialists – hierarchy – each specialist is responsible for establishing a – each specialist is responsible for establishing a hypothesis hypothesis – – a subspecialist a subspecialist represents a more detailed represents a more detailed hypothesis than its parent hypothesis than its parent � Processing Processing � – establish the high level hypothesis (typically using the high level hypothesis (typically using – establish a structured matcher) a structured matcher) – Ask subspecialists subspecialists to to refine refine to a more detailed to a more detailed – Ask hypothesis hypothesis 14

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Classes of Design Classes of Design � Creative Design Creative Design � � Innovative Design Innovative Design � � Routine Design Routine Design � 17

Routine Design Routine Design A method for performing “ “Routine Design Routine Design” ” A method for performing pioneered by David Brown (WPI) for pioneered by David Brown (WPI) for performing design under repetitive well performing design under repetitive well understood situations understood situations 18

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Routine Design Specialists Routine Design Specialists Design Performed by a hierarchy of Design Performed by a hierarchy of cooperating specialists cooperating specialists Specialist S1 Plan Plan • • • Planning Decision Planning Decision Constraint Constraint Call Specialist S2 Call Specialist S2, S3 Specialist S2 Specialist S3 Plan Plan • • • Plan Plan • • • Planning Decision Planning Decision Planning Decision Planning Decision Constraint Constraint Constraint Constraint 20

Routine Design Plans Routine Design Plans � Plans represent a step by step method for Plans represent a step by step method for � performing the design performing the design � A plan may include: A plan may include: � – the use of other specialists the use of other specialists – – tasks to be performed tasks to be performed – 21

Plan Sponsors Plan Sponsors � Each plan is associated with a sponsor Each plan is associated with a sponsor � � A sponsor utilizes a structured matcher to A sponsor utilizes a structured matcher to � assign an applicability rating to its plan assign an applicability rating to its plan � Applicability ratings may be: Applicability ratings may be: � – perfect perfect – – suitable suitable – – neutral neutral – – rule rule- -out out – 22

Plan Selectors Plan Selectors � Problem Problem- -solving agents available to solving agents available to � specialists specialists � Use domain knowledge in consultation with Use domain knowledge in consultation with � plan sponsors to select a plan for execution plan sponsors to select a plan for execution 23

Design Tasks Design Tasks � A task is an ordered collection of design A task is an ordered collection of design � steps steps 24

Design Steps Design Steps � A step is the basic problem solving unit in A step is the basic problem solving unit in � routine design routine design � A step utilizes a structured matcher to A step utilizes a structured matcher to � assign a value to a design attribute assign a value to a design attribute 25