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Information Retrieval

Information Retrieval. Concerned with the: Representation of Storage of Organization of, and Access to Information items. Motivation. Focus is on the user information need Example user information need:

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Information Retrieval

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  1. Information Retrieval • Concerned with the: • Representation of • Storage of • Organization of, and • Access to • Information items.

  2. Motivation • Focus is on the user information need • Example user information need: • Find all docs containing information on college tennis teams which: (1) are maintained by a USA university and (2) participate in the NCAA tournament. • Emphasis is on the retrieval of information (not data)

  3. Data vs. Information Retrieval • Data retrieval • Task: which docs contain a set ofkeywords? (think database) • Well defined semantics • A single erroneous object implies failure! • Information retrieval • Task: get information about a subjector topic – task is user’s task rather than system’s task • Semantics are frequently loose • Errors are unavoidable and tolerated • IR system: • Interpret contents of information items • Generate a ranking which reflects relevance • Notion of relevance is most important

  4. Brief History of IR IR began with human systems Information Collections • Indexed • Searched • Selected by humans.

  5. Brief History of IR • IR as a CS field (80s & early 90s): • classification andcategorization • systems and languages • user interfacesand visualization Still, area was seen as of narrow interest

  6. Recent History of IR Advent of the Web changed this perception • universal repositoryof knowledge • free (low cost)universal access • no editorial board • many problems:IR seen as key to finding the solutions! Increased capability for sharing personal collections of text and other media

  7. Retrieval Database Browsing User Activity in Information Tasks • The User Task • Retrieval • information or data • precise request, purposeful • Browsing • glancing around • navigation through associations

  8. structure Full text Index terms Working with Text • Logical view of the documents • Document representation viewed as a continuum from unprocessed text to a representation of documents’ semantic content Accents spacing Noun groups Manual indexing Docs stopwords stemming structure

  9. Working with Other Media Retrieval of other media is by: • Similarity with example • Human attached metadata • Automatically assigned metadata

  10. The Retrieval Process Content User Interface user need Content Content Processing & Operations logical view logical view Query Operations DB Manager Module Indexing user feedback inverted file query Searching Index retrieved docs Content Database Ranking ranked docs

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