1. A computer system adapted to synthesize a sentence into an output language, the computer system comprising: a lexical synthesizer adapted to perform a lexical selection on a language-independent semantic structure of the sentence using semantic descriptions and lexical descriptions of the output language, wherein the lexical synthesizer is adapted to apply semantic structure correction rules to the language-independent semantic structure to overcome asymmetries between the language-independent semantic structure and the syntactic structure of the sentence in the output language, and wherein the semantic descriptions and the lexical descriptions of the output language are combined into lexical-semantic descriptions; a surface structure builder adapted to build a surface structure of an output sentence in the output language from the language-independent semantic structure using syntactic descriptions and morphological descriptions of the output language, wherein the surface structure of the output sentence is built at least in part based on ratings of syntactic constructions for elements of the source sentence; a morphological synthesizer adapted to perform a morphological synthesis on the surface structure of the output sentence in the output language using morphological descriptions of the output language and to construct the output sentence in the output language; and a linear order synthesizer adapted to determine a linear order for and restore movements on the syntactic structure of the output sentence in the output language.