Desingning FC Rule-Based Systems Designing Forward-Chaining Rule-Based Systems Instructor: Mr. Halavati By: Shahin Jabbari Arfaee Pooya Esfandiar 7/2/20151

Desingning FC Rule-Based Systems

Designing Forward-Chaining Rule-Based

Systems

Instructor:Mr. Halavati

By:Shahin Jabbari Arfaee

Pooya Esfandiar

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• Introduction• General Design Methodologies for FC Systems

Project objective definitionThe major issuesHow experts recommend using available informationDevelopment tasks

• Automobile Diagnostics DomainMost diagnostic ES used BC because most problems had a

finite number of possible faultsDiagnostic problem with an automobile (many possible

faults)

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Tasks in Developing an FC System

1. Define the problem2. Define input data3. Define data-driven structure4. Write initial code5. Test the system6. Design the interface7. Expand the system8. Evaluate the system

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Task 1: Define the Problem

• The initial design step like BC• In our problem: learn about automobile diagnostics

by locate a good car mechanic as an expert• Alternative approach: use a “troubleshooting”

manual probably written by an expert

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Manuals

• Repair ManualsFor many diagnostic problems Can aid problem troubleshootingStep-by-step series of test to isolate the problem

• Shortcomings:The manual must be readily availableThe manual must be easy to followSome one must maintain the manual

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Manuals (Cont’d)

• Auto Repair ManualsMany excellent ones existHelp to identify and repair various car problemsMost have a troubleshooting section The troubleshooting section is divided according to the

principal problems

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Manuals (Cont’d)

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Manuals (Cont’d)

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Manuals (Cont’d)

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Task1 (Cont’d)

• Problem SpecificationAfter developing the system’s structure to address this

problem, we should have a good idea of how to manage other possible car problems

Our problem specification:Address problem associated with “engine won’t start”Address only “cranking system” problems

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Task 2: Define Input Data• Every FC system need some initial data to get started• Write rules whose only task is to ask for some

information about the questionRule 1 start diagnosis

IF Task IS beginTHEN ASK Car problem

Car won’t startCar hesitates at high speedsCar idles rough…

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Task 3: Define Data-Driven Structure

• FC system works by firing rules (using working memory)IF ATHEN Infer or do something

• Adequate result in small applications• Manual => Decision Tree => Rules

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Task 3: Define Data-Driven Structure (Cont’d)

• In our problemIF Task is test battery connection → TESTAND Lights do not brighten → RESULTSTHEN Task is test battery → PROCEED TO

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Task 4: Write Initial Code

• Determine if we have effectively captured the problem’s knowledge

• A good rule structure provides:– correct results – a template to follow rules

RULE test cranking systemIF Car problem IS car won’t startTHEN Task IS test cranking system

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Task 4: Write Initial Code (Cont’d)

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Task 5: Test the System

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• Typical Tests

• A snapshot:

System: Please turn on the ignition.

How does the engine turn?

1) Slowly or not at all

2) Normally

User: Normally


Task 6: Design the Interface

• Attention to Interface after most of knowledge base has been complete

• Begin early and develop it in parallel with the development of knowledge base

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Task 6: Design the Interface (Cont’d)

Dynamic GUI• ES’s were text based• Today shells offerfeatures to customizethe interface

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Task 6: Design the Interface (Cont’d)Dynamic Graphical Interface (Cont’d)• Knowledge base contains:

Information that is displayed on the interfaceFC rules that works with the information

IF Inc SpeedTHEN Speed = Speed + 5AND Speed increase

IF Speed increaseTHEN Temperature = (Speed * 2) + 200AND Oil pressure = (Speed * 0.5) + 40

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Task 6: Design the Interface (cont’d)

• Screen ContentsDisplay Screens

Introduction ScreenIntermediate Finding ScreenConclusion Screen

Question Screen

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Task 7: Expand the System

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• Developing additional rules!

• => additional screens


Task 8: Evaluate the System

• The evaluation is concerned with testing the prototype with some real test case

• Turn to our Expert for the test case!

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Task 8: Evaluate the System (Cont’d)

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Task 8: Evaluate the System (Cont’d)

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Summary on FC design

• The design of FC expert systems is a highly iterative process.

• The systems should be tested immediately after introduction of new rules

• FC inference is preferred over BC if either the goals are not known a priori or their number is very large.

• Defining the initial data is the starting point for a FC design process.

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Summary on FC design (Cont’d)

• Rules used in FC system keeps track of the state of the problem solving

• Design of the system’s interface should begin early in the project and develop in parallel

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Thank you for your patience!

• Any Question?

Documents

Desingning FC Rule-Based Systems Designing Forward-Chaining Rule-Based Systems Instructor: Mr. Halavati By: Shahin Jabbari Arfaee Pooya Esfandiar 7/2/20151