Case-Based Solution Diversity

Alexandra ComanHéctor Muñoz-Avila

Dept. of Computer Science & Engineering

Lehigh UniversitySources:• cbrwiki.fdi.ucm.es/• www.iiia.csic.es/People/enric/AICom.html• www.cse.lehigh.edu/~munoz/CSE335/ • www.aic.nrl.navy.mil/~aha/slides/• http://www.csi.ucd.ie/users/barry-smyth• http://www.csi.ucd.ie/users/lorraine-mcginty

Outline Lehigh University The InSyTe Laboratory Overview of Case-Based Reasoning

Similarity Retrieval Adaptation

Conversational Case-based reasoning Diversity versus Similarity General versus Episodic Knowledge Final Remarks

Synthetizing Diversity Showcasing diverse solutions: success story in recommender systems

(Smyth, Burke, McGinty …) Plan diversity:

Definition of the problem: quantitative vs qualitiative (Myers, AAAI-01) Generating two or more quantitative different plans for same problem

(Srivastava et al, IJCAI-07) Synthetizing diversity:

Case-based retrieval and adaptation from plan library (Coman & Munoz-Avila, ICCBR-10; 11 – under review )

Generating two or more qualitatively different plans for same problem (Coman & Munoz-Avila, AAAI-11)

Our common solution: S: diverse solutions so far, s: candidate solution, P: new problem

sim(s,P) + relativeDiversity(s,S) What changes: S, s, P, sim(), D(s,s’)

11

Research Program: Synthetizing Diversity

Plan Diversity Case-based plan diversitypreliminary work:

New insight: sim(s,P) + relativeDiversity(s,S)

Proposed idea: sim(s,P) + relativeDiversity(s,S) + cost(s)

Danger: don’t want it to be a planning proposal

Research topics:

• Representation scope of using D() versus qualitative diversity

• Trade-offs of solution:• Diversity versus quality• Diversity versus generation

• Diversity in other paradigms: search (A*)

Focus Point: Diversity in CBR

Traditional Retrieval Approach

Similarity-Based Retrieval Select the k most similar items to

the current query.

Problem Vague queries.

Limited coverage of search space in every cycle of the dialogue.

C2C1

C3Q

Query

Available case

Similar case

Lorraine McGinty and Barry SmythDepartment of Computer Science, University College Dublin

Diversity Enhancement

Lorraine McGinty and Barry SmythDepartment of Computer Science, University College Dublin

Diversity-Enhanced Retrieval Select k items such that they are

both similar to the current query but different from each other.

Providing a wider choice allows for broader coverage of the product space.

Allows many less relevant items to be eliminated.

C2 C3

C1 Q

Query

Available case

Retrieved case

Dangers of Diversity Enhancement

Lorraine McGinty and Barry SmythDepartment of Computer Science, University College Dublin

Leap-Frogging the Target Problems occur when the target

product is rejected as a retrieval candidate on diversity grounds.

Protracted dialogs.

Diversity is problematic in the region of the target product. Use similarity for fine-grained search.

Similarity is problematic when far from the target product. Use diversity to speed-up the search.

T

C2 C3

C1 Q

Final Remarks

Questions?