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Relevance Feedback. Limitations Must yield result within at most 3-4 iterations Users will likely terminate the process sooner User may get irritated at seeing same documents repeated after every iteration It has proven to increase the effectiveness of retrieval.
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Presentation Transcript
Relevance Feedback
- Limitations
- Must yield result within at most 3-4 iterations
- Users will likely terminate the process sooner
- User may get irritated at seeing same documents repeated after every iteration
- It has proven to increase the effectiveness of retrieval
Designing a Relevance Feedback System
- Use positive or negative relevance judgments
- Where to apply relevance judgments (query, profile, document, retrieval algorithm)
- Term weight modification. E.g.,
- Increase the weight for terms that appear in relevant docs
- Add new terms found in relevant docs that are frequently mention in connection with query term
Genetic Algorithms
- Several possible solutions are generated in parallel
- The best few of these solutions is chosen and replicated, while the poor ones eliminated
- Replicated solutions creates a breeding population, from which new solutions arise
- The breeding is accomplished by by an exchange of some of the characteristics of the chosen solutions in a crossover operation
Genetic Algorithms (cont.)
- Hill climbing is avoided by
- Pursue multiple solutions in parallel, and discard the low hills
- Introduce new characteristic values at low rate through mutation process (random exchange)
- Relevance Feedback
- Relieves the user of the burden of assigning term weights
- Begins with no weights. Generates query variants by assigning term weights randomly
Genetic Algorithms (cont.)
- Query variants are vector of query term weights
- Each query variant is used to search the documents in the database
- Evaluate each variant with equation on pg. 226
- The variants with highest value creating the most replications
- The resulting breeding population is developed to the same size as the original population
Natural Language Processing
- Focus on structure more than meaning, consequently problems are
- Syntactic ambiguity e.g., they are visiting relatives
- Deep structure of a sentence e.g., grace
- May or may not be semantically correct e.g., Colorless green ideas sleep furiously
- Syntactic rules do not apply to e.g., boolean queries
Natural Language Processing (cont.)
- Semantic Analysis
- Even more elusie e.g., red herring, carrying coals to Newcastle
- Techniques for Semantic Analysis
- Latent semantic indexing uses multidimensional scaling methods to identify concepts
- Dialogue Analysis involves interaction that each time clarifies further what is to be retrieved
Citation Processing
- Use of cited documents to enhance the description of a primary document
- Some use co-citation as a measure of document similarity I.e., number of papers that cite both
- Bibliographic coupling, when two documents cite the same document
- Design problems: Locating citations, interpretation, eliminate duplicate/useless,
Hypertext Links
- Means of connecting 2 distinct pieces of text
- Consists of an identifier and a pointer
- Possibly aid retrieval by suggesting hyperlinks given in top ranked document retrieved
- Do not follow links from linked documents
- Information Filtering: Eliminate large segments of database from consideration
- Passage Retrieval: Identifying relevant sections within a large document encyclopedia
Image and Sound Processing
- Techniques for evaluating and manipulating images directly
- Voice recognition
- Animation and sound: compare to those in libraries
- Music can use style and then pattern matching
