Information Retrieval

• information retrieval
  • deals with the representation, storage, organization of and access to information items
  • is finding material of an unstructured nature that satisfies an information need from within large collections
• differences between databases and information retrieval
  • data are strongly structured × documents are not
  • documents are meant for human interaction, data are meant for the computer
• central elements of IR: documents, information need, satisfaction of the user
• information definition … what a user gets from documents using his own knowledge
• document definition … a trace that a human is sending to another human
• we have a very large set of documents, very imprecise information need and we need to satisfy it very fast
• the system needs to know the format of the document to make sense of it
• main dimensions of documents
  • physical (form) – to read a digital document, you need suitable tools
  • meaning (content) – context is part of the meaning construction
  • social (medium) – there's an intention behind every document
• document forms
  • media
    • text (types: book, article, letter)
    • image (types: x-ray, photograph, graphic)
    • video
    • structured documents
  • documents can consist of different documents
• user query
  • user's information need expressed using a predefined language
• satisfaction
  • system should be simple to use
  • must give the best possible answers, they must be relevant
  • must return reasonable quantities of answers
  • must be fast
• other factors to take into account
  • user's expertise
  • temporal and geographical need
• relevance
  • at document side: document, surrogate, information
  • at user side: information need, request, query
• IR context