20. september 2006TDT55 - Case-based reasoning1 Retrieval, reuse, revision, and retention in...

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Transcript of 20. september 2006TDT55 - Case-based reasoning1 Retrieval, reuse, revision, and retention in...

  • Retrieval, reuse, revision, and retention in case-based reasoning

    TDT55 - Case-based reasoning

  • IntroductionCBR

    Influenced by cognitive scienceUsage of remindings(This reminds me of something Ive seen before)An important issue is how closely CBR systems should mirror how humans think

    TDT55 - Case-based reasoning

  • IntroductionThe steps of the CBR cycle

    Retrieval in CBR Fetches previous cases that are assumed to be able to contribute to solve the target problem

    Reuse Suggests a solution for the target-case from the solutions of the retrieved cases, possibly with an adaption process to fit the target-case better

    Revision Evaluates the chosen solution with respect to degree of success

    Retention The product of the most recent problem-solving episode is incorporated into the systems knowledge

    TDT55 - Case-based reasoning

  • Retrieval in CBRSimilarity assessment

    Surface features: the features given as a part of the case descriptionSimilarity-based retrieval is retrieval based on similarity of the surface featuresIneffective to scan all cases in the base Foot-print based retrieval Validation

    TDT55 - Case-based reasoning

  • Retrieval in CBRRetrieval performance

    The solution quality is as important as the retrieval speed

    Problems that may influence the quality: inadequate similarity measures noise missing values in cases unknown values in the description of the target problem the heterogenity problem different attributes are used to describe different cases

    Work on how to solve this problem: making the similarity measure be the subject of an adaptive learning process guiding by domain knowledge

    TDT55 - Case-based reasoning

  • Retrieval in CBRAlternatives to similarity-retrieval:

    Adaption-guided retrieval Retrieval of the cases which are easiest to adapt

    Diversity-conscious retrieval Combines similarity and diversity measures to distinguish between cases of great similarity.

    Compromise-driven retrieval A case is more acceptable than another if it is closer to the users query and it involves a subset of the compromises that the other case involves.

    TDT55 - Case-based reasoning

  • Retrieval in CBRAlternatives to similarity-retrieval:

    Order-based retrieval Combine preferred values with preference information such as max and min values, and values that the user would prefer not to consider.

    Explanation-oriented retrieval The goal is to explain how the system reached its conclusions. The easiest way of doing this is to use the explanation of the most similar case.

    TDT55 - Case-based reasoning

  • Reuse and revision in CBRReuse can be as simple as returning the most similar case, butsignificant differences in target problem vs. retrieved case need for adaptionAdaption methods:

    Substitution adaption exchanges parts of the retrieved solution

    Transformation adaption changes the structure of the retrieved solution

    Generative adaption derives the new solution by repeating the method used to derive the solution of the retrieved case

    TDT55 - Case-based reasoning

  • Retention in CBRThe simplest form of retention is to just save the problem case and its solution as a new caseThe utility problem:As the case-base grows, every new case will not lead to a lot of new information (overlaps other cases), but will increase the searching time just as much

    Solution in general: Delete harmful cases from the case base

    Solution in CBR: Use a competence-model to decide each cases contribution to the total problem solving competence

    TDT55 - Case-based reasoning

  • Retention in CBRCase-base maintenance

    Insert two new steps into the CBR cycle:Review checks the quality of the system knowledgeRestore chooses and executes maintenance operations

    Categorization of maintenance policies: how they gather data relevant to maintenance decisions how they determine when to trigger maintenance operations the types of maintenance operations available how the maintenance operations are executed

    TDT55 - Case-based reasoning

  • ConclusionsThere is a significant amount of ongoing research on this subjectA lot of the research is motivated by awareness of the limitations of the traditional approach

    TDT55 - Case-based reasoning