Latent semantic analysis for application in a question answer system

1. A system for estimating similarity between concepts comprising:

one or more content sources providing content;

a programmed processor device for coupling to said content sources and configured to:

receive a set of concepts related to a corpus of text documents in a content source;

create 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

derive, 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.

2. The system as claimed in claim 1 , wherein to propagate a vector of a concept against said graph structure, said processor device is further configured to: average the LSA vectors neighboring said concept.

3. The system as claimed in claim 1 , wherein a content source includes a knowledgebase (KB), said representative graph structure being generated from ontologies found in the KB.

4. The system as claimed in claim 3 , wherein said knowledgebase includes a medical knowledgebase.

5. The system as claimed in claim 3 , wherein said created graph structure is an undirected graph generated from ontologies found in the KB, said created graph showing the relations of concepts weighted by a number of relations, wherein each edge between related concepts is a weight representing the number of relations.

6. The system as claimed in claim 5 , wherein a semantic relation includes an ISA relation.

7. The system as claimed in claim 5 , wherein to derive said undirected graph, said processor device is further configured to: collapse each of different relations between concepts in the knowledge base.

8. The system as claimed in claim 5 , wherein to propagate a vector of a concept against said graph structure, said processor device is further configured to:

for a known LSA concept vector c i , apply a formula against data of said undirected graph, said formula comprising:

c

->

i

′

=

c

->

i

+

∑

c

i

∈

N

⁡

(

c

)

⁢

c

->

i

⁢

w

⁡

(

c

,

c

i

)

d

⁡

(

c

i

)

_

_

where c is a neighbor vector concept, {right arrow over (c)} i is the concept vector propagated against the graph, {right arrow over (c)}′ i is a new concept vector, w(c, c i ) is the number of semantic relations involving concepts c and c i , and d(c) is an average vector.

9. The system as claimed in claim 8 , wherein to apply the vector propagation formula, said processor device is further configured to: given a concept vector “c”,

identifying the vectors for the concept in graph;

computing an average of those identified vectors, and

replacing the original concept vector c with new vector average.

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.

12. The computer program product as claimed in claim 10 , wherein said corpus of text documents includes a knowledgebase (KB), said representative graph structure being generated from ontologies found in the KB.

13. The computer program product as claimed in claim 12 , wherein said created graph structure is an undirected graph generated from ontologies found in the KB, said created graph showing the relations of concepts weighted by a number of relations, wherein each edge between related concepts is a weight representing the number of relations.

14. The computer program product as claimed in claim 13 , wherein said vector propagating comprises:

for a known LSA concept vector c i , applying a formula against data of said undirected graph, said formula comprising:

c

->

i

′

=

c

->

i

+

∑

c

i

∈

N

⁡

(

c

)

⁢

c

->

i

⁢

w

⁡

(

c

,

c

i

)

d

⁡

(

c

i

)

_

_

where c is a neighbor vector concept, {right arrow over (c)} i is the concept vector propagated against the graph, {right arrow over (c)}′ i is a new concept vector, w(c, c i ) is the number of semantic relations involving concepts c and c i , and d(c) is an average vector.

15. The computer program product as claimed in claim 14 , wherein the applying said vector propagation formula comprises: given a concept vector “c”,

identifying the vectors for the concept in graph;

computing an average of those identified vectors, and

replacing the original concept vector c with new vector average.