The document proposes a query expansion technique called Nereau that combines traditional query expansion, data from social websites, semantic metadata, and basic user personalization. Experimental evaluations on TREC, ODP, and real user web search sessions show that Nereau outperforms traditional query expansion and search engines. Future work could incorporate more social data, address the dynamic nature of folksonomies, and automatically assign tags when no social data is available.

1. Folksonomy-Based Adaptive
Query Expansion
Claudio Biancalana, Fabio Gasparetti, Alessandro Micarelli,
Alfonso Miola, and Giuseppe Sansonetti
Department of Computer Science and Automation
Artificial Intelligence Laboratory, Roma Tre University
Via della Vasca Navale, 79, 00146 Rome, Italy
SRS 2012 – Montreal, Canada, July 17, 2012

2. State of the Art
• 1993 - Web Search Engines
• Popular techniques to improve their performance
 Explicit Relevance Feedback and (Automatic) Query Expansion
(Maron Kuhns 1960, Rocchio 1971)
 PageRank (1998)
 (Implicitly built) User Profiles (2004)
• e.g., Google Personalized
 Exploiting Social Networks or Signals (2010)
• Facebook, YouTube, Twitter
 Implicitly Understanding User Actions
SRS 2012 – Montreal, Canada, July 17, 2012

3. Query Expansion
The process of expanding a user query with additional
related words and phrases
 Original Query Q: {q1, q2,…, qk, qk+1,…, qn}
 Terms to Add Q+: {e1, e2,..., em}
 Terms to Remove Q-: {qk+1,..., qn}
Expanded Query
EQ = (Q U Q+) - Q-
{q1,q2,...,qk,e1,e2,...,em}
SRS 2012 – Montreal, Canada, July 17, 2012

4. Building a Co-Occ Matrix
For each document, a co-occurrence matrix is
generated and then summed up in a single matrix
 Usually a POS tagger extracts nouns, proper nouns, and
adjectives
t1 t2 t3 t4 t5
t1 0.0 1.0 0.0 2.0 1.0
t2 1.0 0.0 3.0 2.0 0.0
t3 0.0 3.0 0.0 9.0 0.0
t4 2.0 2.0 9.0 0.0 4.0
t5 1.0 0.0 0.0 4.0 0.0
Co-Occurrence Matrix
SRS 2012 – Montreal, Canada, July 17, 2012

5. Limits of Co-Occ Matrices
• Furnas’ Vocabulary problem (1987)
 Polysemy and Homonym
• Mouth (river-sea; cave entrance; body part)
• River Bank or Financial Bank
• Corpus-dependent
 Small corpora contain few statistics
 Relevant concepts missing
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6. Research Question
Is it possible to combine Query Expansion,
Social Web, Semantic Search, and User
Personalization in traditional Web search tools?
SRS 2012 – Montreal, Canada, July 17, 2012

7. Nereau
Nereau, Master of Spiders, is the name of a divinity worshipped in the Nauru
islands, in Micronesia. It is a foremost figure in many myths, some of which
give it a specific role, that of endowing the mad with rationality and the mute
with speech, thus making them complete human beings.
SRS 2012 – Montreal, Canada, July 17, 2012

8. Nereau Co-Occurrence Matrix
• Extension of Co-occurrence matrix:
 Semantic meta-data as 3rd dimension
 The user matrix is built on usage data
• Use of Social Bookmarking Services for metadata
retrieval:
 e.g., delicious, StumbleUpon, Digg
SRS 2012 – Montreal, Canada, July 17, 2012

9. Nereau Co-Occurrence Matrix
• Tags associated with visited URLs are collected
and associated to the (stemmed) keywords from
extracted content.
• Each co-occ matrix is associated to a tag
<t1, t2, tag, co-occ>
SRS 2012 – Montreal, Canada, July 17, 2012

10. Nereau Co-Occurrence Matrix
• The expansion follows similar steps: each term of
the query retrieves multiple co-occ matrices
associated to different tags
• The occs of the tags are summed up over all the
query terms obtaining a weighted set:
SRS 2012 – Montreal, Canada, July 17, 2012

11. Nereau Co-Occurrence Matrix
The co-occ keywords associated to the most relevant
tags compose the new query
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12. Experimental Evaluations
Does it work?
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13. Experimental Evaluations
• Three kinds of evaluations
 TREC corpus-based (500K docs, 249 queries)
• RF vs CoOcc vs Google vs Nereau
 ODP corpus-based
• RF vs CoOcc vs Google vs Nereau
 Web user-based
• Google vs PersGoogle vs RF vs Nereau
• nDCG, P@n, MAP
SRS 2012 – Montreal, Canada, July 17, 2012

14. Experimental Evaluations
Web corpus
Web corpus
42 users on real Web
sessions
nDCG@{1,5,10}
SRS 2012 – Montreal, Canada, July 17, 2012

15. Conclusions and Future Work
• A Nereau search engine that combines:
 Traditional Query Expansion
 Social Web
 Semantic Spaces
 Basic User Personalization
• Suitable to be included in traditional search engines;
 Complexity O(n2K)
 n = training docs
 K = keywords extracted
• Future Work
 Including more social data (e.g., networks, user authority)
 Addressing the dynamic of folksonomies
 Automatically assign tags when no social data is available
SRS 2012 – Montreal, Canada, July 17, 2012