Support for grammar inflections within a software development framework
A natural language understanding server includes grammars specified in a modified extended Backus-Naur form (MEBNF) that includes an agglutination metasymbol not supported by conventional EBNF grammar parsers, as well as an agglutination preprocessor. The agglutination preprocessor applies one or more sets of agglutination rewrite rules to the MEBNF grammars, transforming them to EBNF grammars that can be processed by conventional EBNF grammar parsers. Permitting grammars to be specified in MEBNF form greatly simplifies the authoring and maintenance of grammars supporting inflected forms of words in the languages described by the grammars.
1. A computer-implemented method of transforming modified Extended Backus-Naur Form (MEBNF) phrase grammars, the computer-implemented method comprising:
obtaining, from a software developer, a MEBNF grammar whose rules contain at least one agglutination metasymbol distinct from standard EBNF metasymbols;
storing a plurality of agglutination rewrite rules, each agglutination rewrite rule when applied to a MEBNF expression producing a transformed MEBNF expression, while preserving the language generated by the MEBNF grammar;
transforming the MEBNF grammar to an equivalent EBNF grammar by applying the agglutination rewrite rules to rules of the MEBNF grammar one or more times, wherein each application of an agglutination rewrite rule to a rule of the MEBNF grammar:
removes an agglutination metasymbol from the grammar rule;
adds zero or more agglutination metasymbols to the grammar rule;
wherein the rules of the transformed MEBNF grammar no longer contain an agglutination metasymbol;
receiving a natural language query of a user;
parsing the natural language query using the equivalent EBNF grammar; and
performing an action on behalf of the user based on a result of the parsing.
2. The computer-implemented method of claim 1 , wherein the agglutination rewrite rules specify that the agglutination of two terminal strings is their string concatenation.
3. The computer-implemented method of claim 1 , wherein all instances of an agglutination metasymbol in a rewrite rule are followed by a terminal suffix or preceded by a terminal prefix.
4. The computer-implemented method of claim 1 , further comprising parsing the transformed MEBNF grammar with a conventional EBNF parser.
5. The computer-implemented method of claim 1 , wherein the received rules of the MEBNF grammar specify possessive forms for nouns.
6. The computer-implemented method of claim 1 , wherein the received rules of the MEBNF specify plurals for nouns.
7. The computer-implemented method of claim 1 , wherein the received rules of the MEBNF specify conjugations of verbs.
8. The computer-implemented method of claim 1 , wherein the received rules of the MEBNF specify prefix articles of nouns.
9. A non-transitory computer-readable storage medium storing executable program instructions that when executed by a computer processor perform actions comprising:
obtaining, from a software developer, a modified Extended Backus-Naur Form (MEBNF) grammar whose rules contain at least one agglutination metasymbol distinct from standard EBNF metasymbols;
storing a plurality of agglutination rewrite rules, each agglutination rewrite rule when applied to a MEBNF expression producing a transformed MEBNF expression, while preserving the language generated by the MEBNF grammar;
transforming the MEBNF grammar to an equivalent EBNF grammar by applying the agglutination rewrite rules to rules of the MEBNF grammar one or more times, wherein each application of an agglutination rewrite rule to a rule of the MEBNF grammar:
removes an agglutination metasymbol from the grammar rule;
adds zero or more agglutination metasymbols to the grammar rule;
wherein the rules of the transformed MEBNF grammar no longer contain an agglutination metasymbol;
receiving a natural language query of a user;
parsing the natural language query using the equivalent EBNF grammar; and
performing an action on behalf of the user based on a result of the parsing.
10. The non-transitory computer-readable storage medium of claim 9 , wherein the agglutination rewrite rules specify that the agglutination of two terminal strings is their string concatenation.
11. The non-transitory computer-readable storage medium of claim 9 , wherein all instances of an agglutination metasymbol in a rewrite rule are followed by a terminal suffix or preceded by a terminal prefix.
12. The non-transitory computer-readable storage medium of claim 9 , the actions further comprising parsing the transformed MEBNF grammar with a conventional EBNF parser.
13. The non-transitory computer-readable storage medium of claim 9 , wherein the received rules of the MEBNF grammar specify possessive forms for nouns.
14. The non-transitory computer-readable storage medium of claim 9 , wherein the received rules of the MEBNF specify plurals for nouns.
15. The non-transitory computer-readable storage medium of claim 9 , wherein the received rules of the MEBNF specify conjugations of verbs.
16. The non-transitory computer-readable storage medium of claim 9 , wherein the received rules of the MEBNF specify prefix articles of nouns.
17. A computer system comprising:
a computer processor; and
a non-transitory computer-readable storage medium storing executable program instructions that when executed by the computer processor perform actions comprising:
obtaining, from a software developer, a modified Extended Backus-Naur Form (MEBNF) grammar whose rules contain at least one agglutination metasymbol distinct from standard EBNF metasymbols;
storing a plurality of agglutination rewrite rules, each agglutination rewrite rule when applied to a MEBNF expression producing a transformed MEBNF expression, while preserving the language generated by the MEBNF grammar;
transforming the MEBNF grammar to an equivalent EBNF grammar by applying the agglutination rewrite rules to rules of the MEBNF grammar one or more times, wherein each application of an agglutination rewrite rule to a rule of the MEBNF grammar:
removes an agglutination metasymbol from the grammar rule;
adds zero or more agglutination metasymbols to the grammar rule;
wherein the rules of the transformed MEBNF grammar no longer contain an agglutination metasymbol;
receiving a natural language query of a user;
parsing the natural language query using the equivalent EBNF grammar; and
performing an action on behalf of the user based on a result of the parsing.
18. The computer system of claim 17 , wherein the agglutination rewrite rules specify that the agglutination of two terminal strings is their string concatenation.
19. The computer system of claim 17 , wherein all instances of an agglutination metasymbol in a rewrite rule are followed by a terminal suffix or preceded by a terminal prefix.
20. The computer system of claim 17 , the actions further comprising parsing the transformed MEBNF grammar with a conventional EBNF parser.