Archive for 2004

Using Language Models for Information Retrieval

Monday, December 20th, 2004, posted by Djoerd Hiemstra

Because of the world wide web, information retrieval systems are now used by millions of untrained users all over the world. The search engines that perform the information retrieval tasks, often retrieve thousands of potentially interesting documents to a query. The documents should be ranked in decreasing order of relevance in order to be useful to the user. This book describes a mathematical model of information retrieval based on the use of statistical language models. The approach uses simple document-based unigram models to compute for each document the probability that it generates the query. This probability is used to rank the documents. The study makes the following research contributions.

  • The development of a model that integrates term weighting, relevance feedback and structured queries.
  • The development of a model that supports multiple representations of a request or information need by integrating a statistical translation model.
  • The development of a model that supports multiple representations of a document, for instance by allowing proximity searches or searches for terms from a particular record field (e.g. a search for terms from the title).
  • A mathematical interpretation of stop word removal and stemming.
  • A mathematical interpretation of operators for mandatory terms, wildcards and synonyms.
  • A practical comparison of a language model-based retrieval system with similar systems that are based on well-established models and term weighting algorithms in a controlled experiment.
  • The application of the model to cross-language information retrieval and adaptive information filtering, and the evaluation of two prototype systems in a controlled experiment.
Experimental results on three standard tasks show that the language model-based algorithms work as well as, or better than, today’s top-performing retrieval algorithms. The standard tasks investigated are ad-hoc retrieval (when there are no previously retrieved documents to guide the search), retrospective relevance weighting (find the optimum model for a given set of relevant documents), and ad-hoc retrieval using manually formulated Boolean queries. The application to cross-language retrieval and adaptive filtering shows the practical use of respectively structured queries, and relevance feedback.

[download pdf]

Exam Results

Sunday, December 5th, 2004, posted by Djoerd Hiemstra
Correcting of the projects and the exams is delayed until Friday 13 December 2004. My apologies.

Read more on TeleTOP

Example Results Mini Practicum

Wednesday, October 13th, 2004, posted by Djoerd Hiemstra
Example results and additional explanation of the Mini Practicum can now be found in the archive (partially in Dutch).

Read more on TeleTOP

GIS project

Wednesday, September 22nd, 2004, posted by Djoerd Hiemstra
The GIS project description is now available from TeleTOP under Archive. The project is done in groups of two or three students. Deadline for handing in the products: 19 October 2004.

Read more on TeleTOP

“Minipracticum”

Thursday, September 9th, 2004, posted by Djoerd Hiemstra
The mini practicum assignment takes place next Wednesday 15 September 5/6 hour in ZI-Oostzaal (see Roster and Archive). The assignment can be done in roughly 2 hours in pairs of two students. Dead line for submission of the results is: 22 September.

Read more on TeleTOP

Welcome to Advanced Database Systems

Wednesday, August 25th, 2004, posted by Djoerd Hiemstra
Advanced Database Systems is a new course in the CS Master’s. We are in the middle of a gradual transition from using Dutch as our main language to using English. As a result, the Teletop site has a rather odd mixture of Dutch and English. Let me know if this causes any problems.

Read more on TeleTOP