11. The method of claim 8 , wherein generating a set of token pairs includes generating a set of token pairs resulting in a plurality of token pairs having a same keyword.
8. A method, comprising: receiving search query inputs to search a database of data items, the database having a plurality of categories and an associated data dictionary of terms to add to the search query inputs for searching the database; using at least one processor, identifying demand information that is retrieved from query logs maintained for the search query inputs stored in the database, and supply information comprising seller-provided descriptor information for the data items stored in the database; generating a set of token pairs based on the search query inputs, each token pair comprising a keyword from at least one search query input and a token, the token being a synonym of the keyword; applying candidate selection rules to token pairs across the plurality of categories of data items in the database using the demand information and the supply information, generating a set of candidate token pairs; validating the set of candidate token pairs by calculating a divergence measure for each of the candidate token pairs, wherein the candidate token pairs having divergence values exceeding a divergence threshold are valid token pairs wherein calculation of the divergence value comprises: performing a search using a keyword of a candidate token pair as a search criteria; determining a first distribution (P) of search results for the keyword, the first distribution over the plurality of categories; performing a search using a token of the candidate token pair as a search criteria; determining a second distribution (Q) of search results for the token, the second distribution over the plurality of categories; calculating the divergence measure as an Information Radius (IRad) value as: 
 IRad=0.5[ D ( P ∥avg( P,Q ))+ D ( Q ∥avg( P,Q ))], wherein D is Kullback-Liebler divergence calculated as: 
 D ( P∥Q )=Σ P ( i )log( P ( i )/ Q ( i )), wherein avg (P,Q) is an average of the first distribution and the second distribution, and wherein an index i=1, 2, . . . N, and N is the number of categories in the plurality of categories; and entering the validated token pairs into the data dictionary to form an updated data dictionary; and providing the validated token pairs in the updated data dictionary in response to a search query containing a keyword corresponding to at least one entry in the updated data dictionary.