10. A computer program product for estimating similarity between concepts, the computer program product comprising a tangible, non-transitory storage medium readable by a processing circuit and storing instructions run by the processing circuit for performing a method, the method comprising: receiving a set of concepts related to a corpus of text documents; creating a representative graph structure having graph nodes each representing a latent semantic analysis (LSA) vector associated with a concept, and a node having one or more graph edges, each graph edge representing a strength of a relation between concepts based on an ontology; and deriving, for a concept, a new or modified vector represented by a node in the graph by propagating the LSA vectors against said graph structure, said new or modified vector representing a modified estimated similarity between concepts, wherein the storage medium readable by a processing circuit is not only a propagating signal.
10. A computer program product for estimating similarity between concepts, the computer program product comprising a tangible, non-transitory storage medium readable by a processing circuit and storing instructions run by the processing circuit for performing a method, the method comprising: receiving a set of concepts related to a corpus of text documents; creating a representative graph structure having graph nodes each representing a latent semantic analysis (LSA) vector associated with a concept, and a node having one or more graph edges, each graph edge representing a strength of a relation between concepts based on an ontology; and deriving, for a concept, a new or modified vector represented by a node in the graph by propagating the LSA vectors against said graph structure, said new or modified vector representing a modified estimated similarity between concepts, wherein the storage medium readable by a processing circuit is not only a propagating signal. 11. The computer program product as claimed in claim 10 , wherein said propagating a vector of a concept against said graph structure includes averaging the LSA vectors neighboring said concept.