Public Library Mngmt - Information Retrieval


In the vast expanse of information generated in today’s world, it is indeed very challenging to retrieve the exact required information in the shortest possible time. New technology and computerized searching techniques are aiding information retrieval to be fast yet reliable. Today, the users can use one of the two tools for information retrieval: catalog or indexing service.

What is an Index?

In the domain of library and documentation, the term index is a list of words or headings with associated pointers or locators. The access points are the most relevant subject headings and the pointers are the page numbers, paragraph or section numbers.

An index is useful to find out the material related to that heading in a document, collection of documents, or a library.

What is Indexing?

Indexing is a service that assigns access points to knowledge resources such as books, journals, articles, and documents. Indexing can be done by the author, the editor, or a professional working as an indexer. Index is listed at the end of the book.

Types of Indexing

There are two basic types of indexing depending upon how it is carried out −

  • Manual − performed by humans

  • Automatic − performed by computers

There are also following types of indexing depending upon the way the keywords are coordinated −

  • Precoordinate Indexing − Keywords are coordinated at the time of indexing.

  • Postcoordinate Indexing − Keywords are coordinated at the time of searching.

The subject content needs to be analyzed and then the most appropriate term needs to be produced.

Pre Coordinate Indexing System (PRECIS)

In this indexing system, the search terms are created by the indexer instead of the searcher. The same terms and phrases are used while searching which the indexer assigned to various knowledge resources. The entries are quite descriptive and complex as the terms involve all the related concepts.

Advantages of PRECIS

  • There is no requirement of search logic to a great detail.

  • The users need not get trained for using a particular search query format.

  • It requires no special features in their physical format. Almost all printed indexes reflecting pre-coordinate indexing principles, are hard copy.

  • Concurrent searches are possible.

Disadvantage of PRECIS

  • The relationships among topics once built at the time of index preparation cannot be manipulated. For example, PRECIS are found in journals and bibliographies.

Post Coordinate Indexing System (POCIS)

In this indexing type, the search terms are created not at the time of indexing but at the time of searching to create an index based on the individual search result. Means, the index is created after the complete database is prepared. The searcher has a great control on which terms to combine.

Advantages of POCIS

The following are the advantages of POCIS −

  • It allows the searchers to combine multiple search terms and build their search query.

  • Thus, allows infinite combinations of terms.

  • No fixed sequence of terms is necessary. Each term in the index has equal weight.

Disadvantage of POCIS

The following are the disadvantages of POCIS −

  • It works well only when subject headings are most relevant.
  • It is less precise.

Keyword Indexing

It is a type of indexing that does not have a control on the vocabulary. It is also called natural indexing or free-text indexing. Hans Peter Luhn, a researcher, introduced it in 1950s with the name catchword indexing.

Types of Keyword Indexing

Here are few popular types of keyword indexing −

  • Keyword-in-Context
  • Keyword-out of-Context (KWOC)
  • Keyword-Augmented-in-Context (KWAC)
  • Key Term Alphabetical (KWIC)

Abstract and Abstracting

Abstract is a brief summary produced after analyzing the subject and the written work, which may be in the form of book, research paper, academic document, or similar. Abstract helps the reader to understand the purpose of the work.

An abstract with an index can be described as a key for information retrieval.

Abstracting is a service provided by experts on preparing brief essence of the complete work on a subject or a group of subjects.