17. A machine translation system for translating source text from a first language to target text in a second language, comprising: a library of bi-fragments, each of the bi-fragments including a text fragment from the first language and a text fragment from the second language, at least some of the bi-fragments being modeled as elastic bi-fragments in which words of a fragment are spaced by a gap which is able to assume a variable size corresponding to a number of other words which are to occupy the gap, each of the elastic bi-fragments being associated in memory with a parameter representative of a gap size distribution for the bi-fragment; and a processor which executes instructions for retrieving text fragments from the second language from the library corresponding to text fragments in the source text, generating at least one target hypothesis, each of said target hypotheses comprising text fragments selected from the second language, and evaluating the hypothesis with a translation scoring function which scores the hypothesis according to a plurality of features, at least one of the features comprising a gap size scoring feature which favors hypotheses comprising text fragments with statistically more probable gap sizes over hypotheses with statically less probable gap sizes.
17. A machine translation system for translating source text from a first language to target text in a second language, comprising: a library of bi-fragments, each of the bi-fragments including a text fragment from the first language and a text fragment from the second language, at least some of the bi-fragments being modeled as elastic bi-fragments in which words of a fragment are spaced by a gap which is able to assume a variable size corresponding to a number of other words which are to occupy the gap, each of the elastic bi-fragments being associated in memory with a parameter representative of a gap size distribution for the bi-fragment; and a processor which executes instructions for retrieving text fragments from the second language from the library corresponding to text fragments in the source text, generating at least one target hypothesis, each of said target hypotheses comprising text fragments selected from the second language, and evaluating the hypothesis with a translation scoring function which scores the hypothesis according to a plurality of features, at least one of the features comprising a gap size scoring feature which favors hypotheses comprising text fragments with statistically more probable gap sizes over hypotheses with statically less probable gap sizes. 20. The machine translation system of claim 17 , wherein the library associates each of a plurality of elastic bi-fragments with a corresponding parameter representative of a probability distribution of gaps in at least one of the source text fragment and the target text fragment.