IR systems compute the similarity between two documents by determining which words the documents have in common. That is, the relationship between two documents is defined by an identity relation between the words in the document. While this approach has proven quite successful, it suffers from two problems related to the meanings of words. The first of these is polysemy , when a single word has several meanings. The second is synonymy , when different words have the same meanings.
Lexical cohesion is created by the use of lexical cohesive relations.
Lexical chaining is the process of extracting lexically related words from a text. In general, a text will contain several lexical chains, each of which describes some portion of the cohesive structure of the text. These chains can be built using any lexical resource that relates words by their meaning. WordNet is composed of synonym sets or synsets . Each synset contains one or more words that have the same meaning.