1. A computer program product comprising a non-transitory computer readable medium having computer readable program code embodied therewith, comprising: computer readable program code to create an index structure on a computer by parsing a first target string that comprises a first sentence and a second target string that comprises a second sentence that is different from the first sentence; computer readable program code to match said index structure to index structures previously stored on the computer; and computer readable program code to obtain a translation of the first target string and the second target string corresponding to a match between said index structure and said index structures previously stored on the computer, wherein said index structure comprises phrasal and sub-phrasal markers, each marker having a constituent, a constituent name, and a number that corresponds to numbering each node according to a depth-first visit of the first target string and the second target string, wherein parsing the first target string and the second target string comprises dynamically parsing the first target string and the second target string, wherein in response to the match being determined at a higher sub-phrase level, a lower sub-phrase level of the higher sub-phrase level is not parsed, and wherein the index structure comprises a first phrasal marker corresponding to the first target string and a second phrasal marker corresponding to the second target string.