ai-expert - Production or Expert Systems 1 Weaknesses of...

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1 Production or Expert Systems
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2 Weaknesses of Expert Systems Require a lot of detailed knowledge Restrict knowledge domain Not all domain knowledge fits rule format Expert consensus must exist Knowledge acquisition is time consuming Truth maintenance is hard to maintain Forgetting bad facts is hard
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3 Rule-Based Systems Also known as “production systems” or “expert systems” Rule-based systems are one of the most successful AI paradigms Used for synthesis (construction) type systems Also used for analysis (diagnostic or classification) type systems
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4 Rule Format Label R n if condition1 condition2 then action1 action2
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5 Generic System Components Global Database content of working memory (WM) Production Rules knowledge-base for the system Inference Engine rule interpreter and control subsystem
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6 Expert System Architecture Explanation
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7 Forward Chaining Procedure Do until problem is solved or no antecedents match Collect the rules whose antecedents are found in WM. If more than one rule matches use conflict resolution strategy to eliminate all but one Do actions indicated in by rule “fired”
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8 Inference Engine Rulebase Match Factbase Execute Conflict Resolution new rule new fact
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9 Conflict Resolution Strategies Specificity or Maximum Specificity based on number of antecedents matching choose the one with the most matches Physically order the rules hard to add rules to these systems Data ordering arrange problem elements in priority queue use rule dealing with highest priority elements Recency Ordering Data (based on order facts added to WM) Rules (based on rule firings)
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10 Conflict Resolution Strategies Context Limiting partition rulebase into disjoint subsets doing this we can have subsets and we may also have preconditions Execution Time Fire All Application Rules
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11 Bagger An expert system to bag groceries 1. Check order to see if customer has forgotten something. 2. Bag large items with special attention to bagging big bottles first. 3. Bag medium items with special handling of frozen foods. 4. Bag small items putting them wherever there is room.
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12 Bagger For set of rules see the handout The conflict resolution strategy Maximum specificity (can be simulated by careful rule ordering) Context Limiting (needs to set and evaluate context variable)
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13 Rule B1 IF step is check-order there is bag of potato chips there is no soft drink bottle THEN add one bottle of Pepsi to order Rule B2 IF step is check-order THEN discontinue check-order-step start bag-large-items step Rule B3 IF step is bag-large-items there is large item to be bagged there is large bottle to be bagged there is bag with less than 6 large items THEN put large item in bag
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14 Rule B4 IF step is bag-large-items there is large item to be bagged there is bag with less than 6 large items THEN put large item in bag Rule B5
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This note was uploaded on 01/20/2011 for the course CS 6810 taught by Professor Hecker during the Spring '10 term at CSU East Bay.

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ai-expert - Production or Expert Systems 1 Weaknesses of...

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