Natural language processing based on textual polarity

1. A computer program product for performing a textual query by a search engine, comprising a non-transitory tangible storage device having program code embodied therewith, the program code executable by a processor of a computer to perform a method, the method comprising:

receiving, by the processor, an electronic input text having a polarity value;

identifying, by the processor, the polarity value of the electronic input text based on a polarity of a textual element of the electronic input text, wherein the identifying is based on determining that a change in the polarity of the textual element changes the polarity of the electronic input text, and wherein the polarity of the textual element gives a meaning to the electronic input text;

generating, by the processor, a modified electronic input text by replacing the textual element of the electronic input text with a lexical substitute; wherein a polarity value of the modified electronic input text is different from the polarity value of the electronic input text, and wherein a meaning of the modified electronic input text is different from the meaning of the electronic input text;

searching, by the processor, a database using at least a portion of the modified electronic input text as a query; and

receiving, by the processor, search results based on the searching.

2. The computer program product of claim 1 , the method further comprising:

ranking, by the processor, the received search results relative to one another.

3. The computer program product of claim 2 , wherein the ranking is based on the polarity value of the electronic input text relative to polarity values of the received search results.

4. The computer program product of claim 2 , further comprising:

excluding, by the processor, from search results at least one search result having a polarity value that is opposite to the polarity value of the electronic input text.

5. The computer program product of claim 2 , wherein identifying the polarity value of the electronic input text comprises:

detecting, by the processor, a polar word in the electronic input text based on the polar word matching at least one criterion for a polar term; and

identifying, by the processor, the polarity value of the electronic input text based on the detecting.

6. The computer program product of claim 2 , wherein identifying the polarity value of the electronic input text is based on:

generating, by the processor, a predicate-argument structure (PAS) for the electronic input text;

comparing, by the processor, a pattern in the PAS to one or more patterns in a set of pattern matching rules, the set of pattern matching rules comprising predetermined PAS patterns; and

identifying, by the processor, at least one polar word based on the comparing resulting in a match between the pattern in the PAS to at least one of the one or more patterns in the set of pattern matching rules.

7. The computer program product of claim 1 , further comprising:

querying a database using one or more words in the electronic input text;

receiving one or more candidate passages in response to the query; and

scoring the one or more candidate passages.

8. A computer system for performing a textual query by a search engine, comprising:

one or more computer devices each having one or more processors and one or more tangible storage devices; and

a program embodied on at least one of the one or more storage devices, the program having a plurality of program instructions for execution by the one or more processors, the program instructions comprising instructions for:

receiving an electronic input text having a polarity value;

identifying the polarity value of the electronic input text based on a polarity of a textual element of the electronic input text, wherein the identifying is based on determining that a change in the polarity of the textual element changes the polarity of the electronic input text and wherein the polarity of the textual element gives a meaning to the electronic input text;

generating a modified electronic input text by replacing the textual element of the electronic input text with a lexical substitute; wherein a polarity value of the modified electronic input text is different from the polarity value of the electronic input text, and wherein a meaning of the modified electronic input text is different from the meaning of the electronic input text;

searching a database using at least a portion of the modified electronic input text as a query; and

receiving search results based on the searching.

9. The system of claim 8 , further comprising instructions for:

ranking the received search results relative to one another.

10. The system of claim 9 , wherein the ranking is based on the polarity value of the electronic input text relative to polarity values of the received search results.

11. The system of claim 9 , further comprising instructions for:

excluding from search results at least one search result having a polarity value that is opposite to the polarity value of the electronic input text.

12. The system of claim 9 , wherein instructions for identifying the polarity value of the electronic input text comprise instructions for:

detecting a polar word in the electronic input text based on the polar word matching at least one criterion for a polar term; and

identifying the polarity value of the electronic input text based on the detecting.

13. The system of claim 9 , wherein identifying the polarity value of the electronic input text is based on:

generating a predicate-argument structure (PAS) for the electronic input text;

comparing a pattern in the PAS to one or more patterns in a set of pattern matching rules, the set of pattern matching rules comprising predetermined PAS patterns; and

identifying at least one polar word based on the comparing resulting in a match between the pattern in the PAS to at least one of the one or more patterns in the set of pattern matching rules.