Overview
Boolean model is a simple retrieval model based on aggregation theory and Boolean algebra. It is characterized by finding documents that are "true" that are returned to a query term. In this model, a query term is a Boolean expression, including keywords, and logical operators. By boolean expressions, the features of the user want the documentation can be expressed. Since the definition of the collection is very intuitive, the Boolean model provides an information retrieval system user easy to master the framework. The query string is usually entered in a semantic and precise Boolean expression.
Defect
First, its retrieval strategy is based on binary decision criterion (for example, a document is only related and unrelated two) Status), lacks the concept of document rating (RANK), limiting the search function.
Second, although the Boolean expression has precise semantics, it is often difficult to convert the user's information demand into a Boolean expression. In fact, most retrieval users have discovered that the query information exchanges they need. It is not so easy for Boolean.
Remove the above defects, the Boolean model is still the main model in the document database system.
Boolean model defines whether the index surgery is only two states, or there is or does not appear in one document, so that the weight of the index term is expressed as binary (for example,). The query string Q is a traditional Boolean expression. It is assumed to be the separation form of q. It is assumed that it is defined by any separation form, the document is defined as:
if, the Boolean model represents a document Related to the query string (but may not belong to the query result set), otherwise it means that it is not related to the document. The main advantage of the
Boolean model is to have clear and simple forms, while the main defects are completely matched to cause too much or too little result document being returned. It is well known that the weight of the index term has fundamentally enhances the function of the retrieval system, resulting in the production of vector models.