Lexical Navigation is a document search and retrieval system, which allows users to expand or refine a query based on the actual content of the collection of texts in a given domain. A client-server system written in Java allows users to issue queries, have additional terms suggested to them, explore lexical relationships, and view documents based on keywords they contain. The Lexical Navigation methodology constitutes a powerful set of tools for searching large text collections.

Lexical Networks

Lexical networks containing domain-specific vocabularies and relationships are automatically extracted from the collection and play an important role in this navigation process.
Before queries begin, text analysis tools called "Talent"  develop a vocabulary of the ordinary words, proper names, and technical terms by analyzing the entire collection. Additional Talent tools organize the vocabularies into an extensive set of relationships consisting of triples of

<vocabulary-item::relation::vocabulary-item>.

In these relationships, the "vocabulary-items" are used to represent the real-world concepts that they name. The "relations" give either the name or the strength of an association between the related concepts. The entire set of relationships for a collection is organized into a "lexical network," in which the vocabulary items are the nodes and the relations are the links. . LexNav server processes are used to match initial queries and query terms to nodes in the lexical network. The links are used for navigating to nodes of related vocabulary items, which are then returned to client LexNav processes for use in prompting the user during query modification.
 

The Java Server
 

The actual retrieval of information for queries is accomplished by sending the queries to a server process, also written in Java but running on an IBM RS-6000. This server process, in turn, calls any of a number of C programs which perform the queries of the various components of the LexNav system. Each instance of the server then provides a separate connection to the retrieval system and recognizes 6 commands which call programs based on arguments to these commands and receive data from these programs through standard-out. Then the server instance formats and returns these data to the query process on the client workstation.

 

The Lexical Navigator Client
 

This is the Lexical Navigation interface. You can enter queries in the multi-line text box at the top and then either  directly inspect document titles in the right hand list box, or click on the "related concepts" button, which we have done here, to return terms related to the query terms.

Once LexNav has identified these additional terms, you can add any of them to the additional query, but can also investigate them further by querying what sort of relationships exist between these (sometimes surprising) terms and other terms you expect to find in this collection. You can view these relationships graphically by clicking on the "Plot" button, which produces the display shown here for a query on "Oliver North."

 
 For more information, see "What is Lexical Navigation?"