13. A computer system for generating a parser combination by combining at least two language processing parsers comprising at least one formal language processing parser and one natural language processing parser, the computer system comprising: a processor; a memory connected to the processor; and a parser generator for obtaining a declarative description including a plurality of grammar descriptions generated based on characteristics of target text and dynamically generating a parser combination in the memory to selectively parse parts of target text with different parsers by combining parsers each associated with at least one of the plurality of grammar descriptions, and at least one grammar description type means, wherein the at least one grammar description means is selected from the group consisting of: (i) a grammar description type 1 P 1 until P 2 (P 1 U P 2 ) means to parse input character strings by use of a first parser associated with a first grammar description (P 1 ), until finding at least one input character string first acceptable by a second parser associated with a second grammar description (P 2 ) which is parsed by use of the second parser, and (ii) a grammar description type 2 P 1 for P 2 (P 1 F P 2 ) means to parse input character strings in such a manner that a prefix string of input character strings which are acceptable by the second parser associated with the second grammar description (P 2 ), is cut out and stored, the acceptable input character strings are parsed by use of the second parser, and the cut out and stored prefix string is parsed by use of the first parser associated with the first grammar description (P 1 ).
13. A computer system for generating a parser combination by combining at least two language processing parsers comprising at least one formal language processing parser and one natural language processing parser, the computer system comprising: a processor; a memory connected to the processor; and a parser generator for obtaining a declarative description including a plurality of grammar descriptions generated based on characteristics of target text and dynamically generating a parser combination in the memory to selectively parse parts of target text with different parsers by combining parsers each associated with at least one of the plurality of grammar descriptions, and at least one grammar description type means, wherein the at least one grammar description means is selected from the group consisting of: (i) a grammar description type 1 P 1 until P 2 (P 1 U P 2 ) means to parse input character strings by use of a first parser associated with a first grammar description (P 1 ), until finding at least one input character string first acceptable by a second parser associated with a second grammar description (P 2 ) which is parsed by use of the second parser, and (ii) a grammar description type 2 P 1 for P 2 (P 1 F P 2 ) means to parse input character strings in such a manner that a prefix string of input character strings which are acceptable by the second parser associated with the second grammar description (P 2 ), is cut out and stored, the acceptable input character strings are parsed by use of the second parser, and the cut out and stored prefix string is parsed by use of the first parser associated with the first grammar description (P 1 ). 15. The computer system according to claim 13 , wherein the computer system further comprises: an editing unit for describing a declarative description including multiple grammar descriptions; and an interpretation unit for identifying a combination of grammar descriptions included in the declarative description by parsing the declarative description, wherein the grammar descriptions include at least one of the grammar description types 1 (P 1 U P 2 ) and 2 (P 1 F P 2 ); wherein the parser generator generates a parser combination by combining parsers associated, respectively, with the grammar descriptions identified by the interpretation unit.