Computational Semantics Scott Farrar CLMA, University of Washington far- rar@u.washington.edu Computational Semantics Computational semantics Logic First-Order Scott Farrar Predicate logic CLMA, University of Washington farrar@u.washington.edu February 12, 2010 1/27
Computational Today’s lecture Semantics Scott Farrar CLMA, University of Washington far- rar@u.washington.edu Computational semantics Computational semantics 1 Logic First-Order Predicate logic Logic 2 First-Order Predicate logic 3 2/27
Computational Definition Semantics Computational semantics refers to the task whereby the Scott Farrar CLMA, University meanings of natural language utterances are automatically of Washington far- rar@u.washington.edu computed and manipulated according to some logical system. Computational semantics Logic First-Order Predicate logic 3/27
Computational Definition Semantics Computational semantics refers to the task whereby the Scott Farrar CLMA, University meanings of natural language utterances are automatically of Washington far- rar@u.washington.edu computed and manipulated according to some logical system. Computational semantics Key problem areas in computational semantics: Logic First-Order Predicate logic 3/27
Computational Definition Semantics Computational semantics refers to the task whereby the Scott Farrar CLMA, University meanings of natural language utterances are automatically of Washington far- rar@u.washington.edu computed and manipulated according to some logical system. Computational semantics Key problem areas in computational semantics: Logic First-Order defining a semantic representation ( formalism ) Predicate logic 3/27
Computational Definition Semantics Computational semantics refers to the task whereby the Scott Farrar CLMA, University meanings of natural language utterances are automatically of Washington far- rar@u.washington.edu computed and manipulated according to some logical system. Computational semantics Key problem areas in computational semantics: Logic First-Order defining a semantic representation ( formalism ) Predicate logic defining algorithms for deriving semantics representations from NL input ( semantic analysis ) 3/27
Computational Definition Semantics Computational semantics refers to the task whereby the Scott Farrar CLMA, University meanings of natural language utterances are automatically of Washington far- rar@u.washington.edu computed and manipulated according to some logical system. Computational semantics Key problem areas in computational semantics: Logic First-Order defining a semantic representation ( formalism ) Predicate logic defining algorithms for deriving semantics representations from NL input ( semantic analysis ) defining procedures for performing inferences using those representations ( automated inferencing, reasoning ) 3/27
Computational Definition Semantics Computational semantics refers to the task whereby the Scott Farrar CLMA, University meanings of natural language utterances are automatically of Washington far- rar@u.washington.edu computed and manipulated according to some logical system. Computational semantics Key problem areas in computational semantics: Logic First-Order defining a semantic representation ( formalism ) Predicate logic defining algorithms for deriving semantics representations from NL input ( semantic analysis ) defining procedures for performing inferences using those representations ( automated inferencing, reasoning ) Much overlap with artificial intelligence (AI) research (e.g., SHRDLU, KL-ONE, STRIPS). The task of robust semantic analysis is seen as an AI-complete problem. 3/27
Computational Semantic representation language Semantics Scott Farrar Definition CLMA, University of Washington far- A semantic representation is an unambiguous expression rar@u.washington.edu into which natural language strings are transformed for the Computational purposes of analyzing the meaning of natural language. A semantics Logic good representation language for NLP should be: First-Order Predicate logic 4/27
Computational Semantic representation language Semantics Scott Farrar Definition CLMA, University of Washington far- A semantic representation is an unambiguous expression rar@u.washington.edu into which natural language strings are transformed for the Computational purposes of analyzing the meaning of natural language. A semantics Logic good representation language for NLP should be: First-Order Predicate logic unambiguous (many to one mapping) Even controlled languages are usually ambiguous: CO attaches to hemoglobin in mammals. 4/27
Computational Semantic representation language Semantics Scott Farrar Definition CLMA, University of Washington far- A semantic representation is an unambiguous expression rar@u.washington.edu into which natural language strings are transformed for the Computational purposes of analyzing the meaning of natural language. A semantics Logic good representation language for NLP should be: First-Order Predicate logic unambiguous (many to one mapping) Even controlled languages are usually ambiguous: CO attaches to hemoglobin in mammals. representationally adequate , or expressive enough to handle all natural language phenomena: speaker intention, evidentiality, tense, aspect, coordination, etc. 4/27
Computational Semantic representation language Semantics Scott Farrar Definition CLMA, University of Washington far- A semantic representation is an unambiguous expression rar@u.washington.edu into which natural language strings are transformed for the Computational purposes of analyzing the meaning of natural language. A semantics Logic good representation language for NLP should be: First-Order Predicate logic unambiguous (many to one mapping) Even controlled languages are usually ambiguous: CO attaches to hemoglobin in mammals. representationally adequate , or expressive enough to handle all natural language phenomena: speaker intention, evidentiality, tense, aspect, coordination, etc. compatible with natural language ( naturalness ), but still allow efficient semantic analysis Units of syntax should map onto units of semantic rep. in a straightforward manner. 4/27
Computational Semantic representation language Semantics Scott Farrar A good reasoning procedure for some representation CLMA, University of Washington far- language for NLP should be: rar@u.washington.edu Computational semantics Logic First-Order Predicate logic 5/27
Computational Semantic representation language Semantics Scott Farrar A good reasoning procedure for some representation CLMA, University of Washington far- language for NLP should be: rar@u.washington.edu Computational inferentially adequate , or able to facilitate the kind of semantics reasoning necessary for comp. linguistics Logic The bus almost collided with the small car. First-Order Predicate logic The driver looked drunk. (bus driver, car driver?) 5/27
Computational Semantic representation language Semantics Scott Farrar A good reasoning procedure for some representation CLMA, University of Washington far- language for NLP should be: rar@u.washington.edu Computational inferentially adequate , or able to facilitate the kind of semantics reasoning necessary for comp. linguistics Logic The bus almost collided with the small car. First-Order Predicate logic The driver looked drunk. (bus driver, car driver?) sound : new knowledge actually follows from old knowledge, and is not simply created on the fly (truth preserving) 5/27
Computational Semantic representation language Semantics Scott Farrar A good reasoning procedure for some representation CLMA, University of Washington far- language for NLP should be: rar@u.washington.edu Computational inferentially adequate , or able to facilitate the kind of semantics reasoning necessary for comp. linguistics Logic The bus almost collided with the small car. First-Order Predicate logic The driver looked drunk. (bus driver, car driver?) sound : new knowledge actually follows from old knowledge, and is not simply created on the fly (truth preserving) complete : each and every correct inference can be made (more difficult to achieve than soundness) incomplete reasoning is still useful 5/27
Computational Semantic representation language Semantics Scott Farrar A good reasoning procedure for some representation CLMA, University of Washington far- language for NLP should be: rar@u.washington.edu Computational inferentially adequate , or able to facilitate the kind of semantics reasoning necessary for comp. linguistics Logic The bus almost collided with the small car. First-Order Predicate logic The driver looked drunk. (bus driver, car driver?) sound : new knowledge actually follows from old knowledge, and is not simply created on the fly (truth preserving) complete : each and every correct inference can be made (more difficult to achieve than soundness) incomplete reasoning is still useful tractable , or be able to make inferences in a reasonable amount of time. 5/27
Recommend
More recommend
