Search Results Need to be Diverse Mark Sanderson University of Sheffield

How to have fun while running an evaluation campaign Mark Sanderson University of Sheffield

Aim Tell you about our test collection work in Sheffield How we’ve been having fun building test collections 09/05/2015 3

Organising this is hard TREC Donna, Ellen CLEF Carol NTCIR Noriko Make sure you enjoy it 09/05/2015 4

ImageCLEF Cross language image retrieval Running for 6 years Photo Medical And other tasks Imageclef.org 09/05/2015 5

How do we do it? Organise and conduct research imageCLEFPhoto 2008 Study diversity in search results Diversity? 09/05/2015 6

SIGIR 09/05/2015 7

ACL 09/05/2015 8

Mark Sanderson 09/05/2015 9

Cranfield model 09/05/

Operational search engine Ambiguous queries What is correct interpretation? Don’t know Serve as diverse a range as possible 09/05/

Diversity is studied Carbonell, J. and Goldstein, J. (1998) The use of MMR, diversity-based reranking for reordering documents and producing summaries. In ACM SIGIR, Zhai, C. (2002) Risk Minimization and Language Modeling in Text Retrieval, PhD thesis, Carnegie Mellon University. Chen, H. and Karger, D. R. (2006) Less is more: probabilistic models for retrieving fewer relevant documents. In ACM SIGIR,

Cluster hypothesis “closely associated documents tend to be relevant to the same requests” Van Rijsbergen (1979) 09/05/

Most test collections Focussed topic Relevance judgments Who says what is relevant? (almost always) one person Consideration of interpretations Little or none Gap between test and operation

Few test collections Hersh, W. R. and Over, P. (1999) Trec-8 interactive track report. TREC-8 Over P. (1997) TREC-5 Interactive Track Report. TREC-5, Clarke, C. L., Kolla, M., Cormack, G. V., Vechtomova, O., Ashkan, A., Büttcher, S., and MacKinnon, I. (2008) Novelty and diversity in information retrieval evaluation. In ACM SIGIR. 09/05/

Study diversity What sorts of diversity is there? Ambiguous query words How often is it a feature of search? How often are queries ambiguous? How can we add it into test collections? 09/05/

Extent of diversity? “Ambiguous queries: test collections need more sense”, SIGIR 2008 How do you define ambiguity? Wikipedia WordNet 09/05/

Disambiguation page 09/05/

Wikipedia stats enwiki pages-articles.xml (12.7Gb) Disambiguation pages easy to spot “_(disambiguation)” in title Chicago “{{disambig}}” template George_bush

Conventional source Downloaded WordNet v3.0 88K words 09/05/

Query logs LogUnique queries (all) Most frequent (fr) Year(s) gathered Web1,000,0008, PA507,91414,

Fraction of ambiguous 123 NameWiWNWN+Wi Webfreq7.6%4.0%10.0% all2.5%0.8%3.0% PAfreq10.5%6.4%14.7% all2.1%0.8%2.7%

Conclusions Ambiguity is a problem Ambiguity is present in query logs Not just Web search Ambiguity present? Need for IR systems to produce diverse results 09/05/

Test collections Don’t test for diversity Do search systems deal with it? 09/05/

ImageCLEFPhoto Build a test collection Encourage the study of diversity Study how others deal with diversity Have some fun 09/05/

Collection IAPR TC-12 20,000 travel photographs Text captions 60 existing topics Used in two previous studies 39 used for diversity study 09/05/

Diversity needs in topic “Images of typical Australian animals” 09/05/

Types of diversity 22 geographical “Churches in Brazil” 17 other “Australian animals” 09/05/

Relevance judgments Clustered existing qrels Multiple assessors Good level of agreement on clusters 09/05/

Evaluation Precision at 20 P(20) Fraction of relevant in top 20 Cluster recall at 20 CR(20) Fraction of different clusters in top 20 09/05/

Track was popular 24 groups 200 runs in total 09/05/

Submitted runs 09/05/

Compare with past years Same 39 topics used in 2006, 2007 But without clustering Compare cluster recall on past runs Based on identical P(20) Cluster recall increased Substantially Significantly 09/05/

Meta-analysis This was fun We experimented on participants outputs Not by design Lucky accident 09/05/

Not first to think of this Buckley and Voorhees SIGIR 2000, 2002 Use submitted runs to generate new research 09/05/

Conduct user experiment Do users prefer diversity? Experiment Build a system to do this Show users your system Baseline system Measure users 09/05/

Why bother… …when others have done the work for you Pair up randomly sampled runs High CR(20) Low CR(20) Show to users 09/05/

Animals swimming 09/05/

Numbers 25 topics 31 users 775 result pairs compared 09/05/

User preferences 54.6% more diversified; 19.7% less diversified; 17.4% both were equal; 8.3% preferred neither. 09/05/

Conclusions Diversity appears to be important System don’t do diversity by default Users prefer diverse results Test collections don’t support diversity But can be adapted 09/05/

and Organising evaluation campaigns is rewarding And can generate novel research 09/05/