Dienstag, 5. Mai 2009

[Topic] Centroid based Classification

[1] claimed a very high increase in accuracy due to the use of a different centroid weighting scheme. The weighting scheme extracts the "discriminative" features. The increase is around 0.7-0.10 F1 measure.

[2] Analyzes centroid based learning approaches in detail. k-nn, c4.5 and centroid base approaches are compared. The success of centroid based approaches is explained as comparing the inter class similarity distribution (=Length of the centroid) vs. the average similarity of a new item to all documents (interpretation of centroid based cosine similarity). While the average similarity of a new items do not take term dependencies into account and suffer similar drawbacks than naive bayes algorithms (over estimate of positive term co-occurrences, underestimate of negative term co-occurrences), the second term (=centroid length) addresses the co-occurrence aspect. (see Section 5 of the paper for details)

Further the paper provides: statistical testing of classification results (resampled t-test and sign test)




[1] Guan, Hu and Zhou, Jingyu and Guo, Minyi (2009) A Class-Feature-Centroid Classifier for Text Categorization. In: 18th International World Wide Web Conference, April 20th-24th, 2009, Madrid, Spain.

http://www2009.eprints.org/21/

[2] Han, E. and Karypis, G. 2000. Centroid-Based Document Classification: Analysis and Experimental Results. In Proceedings of the 4th European Conference on Principles of Data Mining and Knowledge Discovery (September 13 - 16, 2000). D. A. Zighed, H. J. Komorowski, and J. M. Zytkow, Eds. Lecture Notes In Computer Science, vol. 1910. Springer-Verlag, London, 424-431.

http://portal.acm.org/citation.cfm?id=669671

Freitag, 1. Mai 2009

[Paper] A comparative Study of Two Short Text Semantic Similarity Measures

    Book Series -
    Book Title  - Agent and Multi-Agent Systems: Technologies and Applications
    Chapter Title  - A Comparative Study of Two Short Text Semantic Similarity Measures
    First Page  - 172
    Last Page  - 181
    Copyright  - 2008
    Author  - James O’Shea
    Author  - Zuhair Bandar
    Author  - Keeley Crockett
    Author  - David McLean
    DOI  - 10.1007/978-3-540-78582-8_18
    Link  - http://www.springerlink.com/content/v0867641u342pm2

James O’SheaContact Information, Zuhair BandarContact Information, Keeley CrockettContact Information and David McLeanContact Information

(1)  Department of Computing and Mathematics, Manchester Metropolitan University, Chester St., Manchester, M1 5GD, United Kingdom
Abstract
This paper describes a comparative study of STASIS and LSA. These measures of semantic similarity can be applied to short texts for use in Conversational Agents (CAs). CAs are computer programs that interact with humans through natural language dialogue. Business organizations have spent large sums of money in recent years developing them for online customer self-service, but achievements have been limited to simple FAQ systems. We believe this is due to the labour-intensive process of scripting, which could be reduced radically by the use of short-text semantic similarity measures. “Short texts” are typically 10-20 words long but are not required to be grammatically correct sentences, for example spoken utterances and text messages. We also present a benchmark data set of 65 sentence pairs with human-derived similarity ratings. This data set is the first of its kind, specifically developed to evaluate such measures and we believe it will be valuable to future researchers.

Keywords  Natural Language - Semantic Similarity - Dialogue Management - User Modeling - Benchmark - Sentence


Important Points

  • Discussion and summary of different kinds of similarities (Taxonomic, related, goal derived and radial)
  • Introduction of a (small) test corpora and how the corpora was created. This includes some discussion on how humans rate.
  • Statement that co-occurrence measures yield also high similarity values for antonyms