Inference over semantic network with some links omitted from indexes

1. An apparatus comprising an inference system ( 109 ), wherein the inference system is responsive to an omission rule ( 108 ) coupled to an index maintainer ( 107 ) for deciding for a link ( 106 ) in a semantic network ( 106 ) whether to include the link in each of the indexes ( 113 ) associated with nodes ( 105 ) that the link references.

2. The apparatus of claim 1 , wherein the inference system comprises a goal-oriented inference system taking omission rules into account as evaluation order constraints.

3. The apparatus of claim 1 , wherein the inference system comprises a goal-oriented inference system wherein goals with open variables are evaluated starting from any constants in argument positions from which links have not been dropped in the applicable index.

4. The apparatus of claim 1 , wherein the inference system comprises a goal-oriented inference system configured to prioritize an inference strategy that avoids trying to follow links from indexes from which some links relevant for the query have been omitted over strategies that try to follow links using such indexes.

5. The apparatus of claim 1 , further comprising an omission rule learner ( 112 ) configured to automatically create, delete, or modify omission rules.

6. The apparatus of claim 5 , wherein the omission rule learner is configured to collect statistics about how frequently a particular link type is followed through an index and create an omission rule that causes links of that type not to be added to the index.

7. The apparatus of claim 1 , wherein the omission rule triggers an existing link to be dropped from an index.

8. The apparatus of claim 7 , wherein the dropping is uses random replacement.

9. The apparatus of claim 7 , wherein the dropping is based on the link leading to a node that has not been visited for a long time.

10. The apparatus of claim 1 , wherein the omission rule decides whether to omit a link from an index based on the size of the index.

11. A method comprising performing, by a processor ( 100 ), inference over a semantic network ( 106 ), wherein the inference is responsive to a link ( 106 ) having been omitted from an index ( 113 ) associated with a node ( 105 ) referenced by the link in the semantic network.

12. The method of claim 11 , wherein the inference is performed using a goal-oriented inference method.

13. The method of claim 11 , wherein the inference prioritizes an inference strategy that avoids trying to follow links from indexes from which a link has been omitted over a strategy that tries to follow links from such indexes.

14. The method of claim 11 , wherein the inference system evaluates a goal starting from a constant in an argument position from which links have not been dropped from the applicable index in response to the goal having such an argument position.

15. A computer program product stored on non-transitory computer-readable medium comprising program code means for causing a computer to perform inference over a semantic network, wherein the inference is responsive to a link having been omitted from an index associated with a node referenced by the link in the semantic network.

16. The computer program product of claim 15 , further comprising program code means for causing the computer to perform goal-oriented inference.

17. The computer program product of claim 15 , wherein the inference prioritizes an inference strategy that avoids trying to follow links from indexes from which a link has been omitted over a strategy that tries to follow links from such indexes.

18. The computer program product of claim 15 , wherein the inference system evaluates a goal starting from a constant in an argument position from which links have not been dropped from the applicable index in response to the goal having such an argument position.