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Precision, recall and specificity

The standard measures for IR are recall and precision. Assuming that:

then precision and recall measures are obtained as follows:

precision = RETREL / RET

recall = RETREL / REL

The basic information unit presented to a user is a search report that contains a partial document text which could be either a linear paragraph or a textual unit when using a hypertext system.

Specificity is concerned with the information or query language of an IR system. Often such a language is:

  1. Not correctly applied by the user;
  2. Not expressive enough for a specific search inquiry.

The first problem is mainly based on the abstractness and complexity of a query language regarding different system users, whereas the second problem is rooted in the complexity of natural language expressions which are part of an inquiry. For example, an inquiry looking for an explanation of stand-by orbital communication system has to identify that stand-by modifies system, in contrast to an inquiry about stand-by power supply system where stand-by modifies power supply instead of system. This becomes more crucial when the inquiries are embedded in Boolean expressions.