Redeeming Relevance for Subject Search in Citation Indexes Shannon Bradshaw The University of Iowa

Citation Indexes Valuable tools for research Examples: SCI, CiteSeer, arXiv, CiteBase Permit traversal of citation networks Identify significant contributions Subject search is often the entry point

Subject search Query similarity Citation frequency

PageRank Example: 2 papers similar in terms of relevance published at roughly the same time Paper A cited only by its author Paper B cited 10 times by other authors Paper B likely to have greater priority for reading

Problem Boolean retrieval metrics Many top documents are not relevant Effective for Web-searches Any one of several popular pages will do Not so for users of citation indexes

Reference Directed Indexing (RDI) Objective: To combine strong measures of both relevance and significance in a single metric Intuition: The opinions of authors who cite a document effectively distinguish both what a document is about and how important a contribution it makes Similar to the use of anchor text to index Web documents

Example Paper by Ron Azuma and Gary Bishop On tracking the heads of users in augmented reality systems Head tracking is necessary in order to generate the correct perspective view

A single reference to Azuma Azuma et al. [2] developed a 6DOF tracking system using linear accelerometers and rate gyroscopes to improve the dynamic registration of an optical beacon ceiling tracker.

Summarizes Azuma paper as… A six degrees of freedom tracking system With additional details: Improves dynamic registration Optical beacon ceiling tracker Linear accelerometers Rate gyroscopes

Leveraging multiple citations For any document cited more than once… We can compare the words of all authors Terms used by many referrers make good index terms for a document

Repeated use of “tracking” and “augmented reality” Whereas several augmented reality environments are known (cf. State et al. 1] Azuma and Bishop [3]) … e.g. landmark tracking for determining head pose in augmented reality [2, 3, 4, 5] Azuma and Holloway analyze sources of registration and tracking errors in AR systems [2, 11, 12]. Azuma et al. [2] developed a 6DOF tracking system using linear accelerometers

A voting technique RDI treats each citing document as a voter The presence of a query term in referential text is a vote of “yes” The absence of that term, a “no” The documents with the most votes for the query terms rank highest

Related Work McBryan – World Wide Web Worm Brin & Page – Google Chakrabarti et. al - CLEVER Mendelzon et. al - TOPIC Bharat et. al – Hilltop Craswell et. al – Effective Site Finding

Contributions Application to scientific literature “Anchor text” for unrestricted subject search “Anchor text” for combining measures of relevance and significance

Rosetta Experimental system in which we implemented RDI Term weighting metric: Ranking metric:

Experiments 10,000 research papers Gathered from CiteSeer Each document cited at least once Evaluated Retrieval precision Impact of search results

Comparison system We compared Rosetta to a traditional content-based retrieval system Comparison system uses TFIDF for term weighting: And the Cosine ranking metric:

Indexing Indexed collection in both Rosetta and the TFIDF/Cosine system Rosetta indexed documents based on references to them The TFIDF/Cosine system indexed documents based on words used within them Required that each document was cited at least once to ensure that both systems indexed the same set of documents

As referential text, Rosetta used CiteSeer’s “contexts of citation”

Queries 32 queries in our test set Queries were key terms extracted from “Keywords” sections of documents Queries extracted from sample of 24 documents Document from which key term was extracted established the topic of interest

Queries

Relevance assessments The topic of interest for a query was the idea identified by the corresponding key term Relevant documents directly addressed this same topic Example: Query: “force feedback” Relevant: Work on providing a sense of touch in VR applications or other computer simulations

Retrieval interface Meta-interface Queried both systems Used top 10 search results from each system Integrated all 20 search results Presented them in random order No way to determine the source of a retrieved document

Experimental summary 32 queries drawn from document key terms Document identified the topic of interest Relevant documents addressed the same topic Used a meta-search interface Evaluated top 10 from both systems Origin of search results hidden

Precision at top 10 On average RDI provided a 16.6% improvement over TFIDF/Cosine 1 or 2 more relevant documents in the top 10 Result is significant t-test of the mean paired difference Test statistic = Significant at a confidence level of 99.5%

Precision at top 10 (cont’d)

Many retrieval errors avoided Example: software architecture diagrams Most papers about software architecture frequently use the term “diagrams” Few are about tools for diagramming TFIDF/Cosine system -- 0/10 relevant Rosetta -- 4/10 relevant (3 in top 5) Rosetta made the correct distinction more often

Rosetta Shortcomings Retrieval metric sorts search results by number of query terms matched Some authors reuse portions of text in which other documents are cited

Impact of search results A look at the number of citations to documents retrieved for each query Compared RDI to a baseline provided by the TFIDF/Cosine system TFIDF/Cosine includes no measure of impact Seeking only a measure of the relative impact of documents retrieved by RDI on a given topic

Experiment For each query… Calculated the average citations/year for each document Average publication year for Rosetta – 1994 TFIDF/Cosine – 1995 Found the median number of citations/year for each set of search results Found the difference between the median for Rosetta and the median for TFIDF/Cosine

Difference in impact On average the median citations/year… 8.9 for Rosetta 1.5 for the baseline

Difference in impact (cont’d)

Summary of Experiments Small study – results are tentative Surpassed retrieval precision of a widely used relevance-based approach Consistently retrieved documents that have had a significant impact

Future Work Retrieval metric that eliminates Boolean component Large scale implementation with CiteSeer data Studies with more sophisticated relevance- based retrieval systems Comparison with popularity-based retrieval techniques

Contact Shannon Bradshaw The University of Iowa