Designing Forward-Chaining Rule-Based SystemsInstructor:Mr. HalavatiBy:Shahin Jabbari ArfaeePooya Esfandiar

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IntroductionGeneral Design Methodologies for FC SystemsProject objective definitionThe major issuesHow experts recommend using available informationDevelopment tasksAutomobile Diagnostics DomainMost diagnostic ES used BC because most problems had a finite number of possible faultsDiagnostic problem with an automobile (many possible faults)**

Tasks in Developing an FC SystemDefine the problemDefine input dataDefine data-driven structureWrite initial codeTest the systemDesign the interfaceExpand the systemEvaluate the system**

Task 1: Define the ProblemThe initial design step like BCIn our problem: learn about automobile diagnostics by locate a good car mechanic as an expertAlternative approach: use a troubleshooting manual probably written by an expert**

ManualsRepair ManualsFor many diagnostic problems Can aid problem troubleshootingStep-by-step series of test to isolate the problemShortcomings:The manual must be readily availableThe manual must be easy to followSome one must maintain the manual**

Manuals (Contd)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**

Manuals (Contd)**

Manuals (Contd)**

Manuals (Contd)**

Task1 (Contd)Problem SpecificationAfter developing the systems structure to address this problem, we should have a good idea of how to manage other possible car problemsOur problem specification:Address problem associated with engine wont startAddress only cranking system problems**

Task 2: Define Input DataEvery FC system need some initial data to get startedWrite rules whose only task is to ask for some information about the questionRule 1 start diagnosis IF Task IS beginTHEN ASK Car problemCar wont startCar hesitates at high speedsCar idles rough**

Task 3: Define Data-Driven StructureFC system works by firing rules (using working memory)IF ATHEN Infer or do somethingAdequate result in small applicationsManual => Decision Tree => Rules**

Task 3: Define Data-Driven Structure (Contd)In our problemIF Task is test battery connection TESTAND Lights do not brighten RESULTSTHEN Task is test battery PROCEED TO**

Task 4: Write Initial CodeDetermine if we have effectively captured the problems knowledgeA good rule structure provides: correct results a template to follow rules

RULE test cranking systemIFCar problem IS car wont startTHEN Task IS test cranking system**

Task 4: Write Initial Code (Contd)**

Task 5: Test the System** Typical Tests A snapshot:System: Please turn on the ignition.How does the engine turn?1) Slowly or not at all2) NormallyUser: Normally

Task 6: Design the InterfaceAttention to Interface after most of knowledge base has been completeBegin early and develop it in parallel with the development of knowledge base**

Task 6: Design the Interface (Contd)Dynamic GUIESs were text basedToday shells offerfeatures to customizethe interface

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Task 6: Design the Interface (Contd)Dynamic Graphical Interface (Contd)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**

Task 6: Design the Interface (contd)Screen ContentsDisplay ScreensIntroduction ScreenIntermediate Finding ScreenConclusion ScreenQuestion Screen**

Task 6: Design the Interface (Contd)**

Task 6: Design the Interface (Contd)**

Task 7: Expand the System** Developing additional rules! => additional screens

Task 8: Evaluate the SystemThe evaluation is concerned with testing the prototype with some real test caseTurn to our Expert for the test case!**

Task 8: Evaluate the System (Contd)**

Task 8: Evaluate the System (Contd)**

Summary on FC designThe design of FC expert systems is a highly iterative process.The systems should be tested immediately after introduction of new rulesFC 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.**

Summary on FC design (Contd)Rules used in FC system keeps track of the state of the problem solvingDesign of the systems interface should begin early in the project and develop in parallel**

Thank you for your patience!Any Question?

*Desingning FC Rule-Based Systems

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