| 摘要 |
A system and method for compiling weighted context-dependent rewrite rules into weighted finite-state transducers introduces context marking symbols only when and where they are needed. In particular, the compiler and compiling method use a composition of five simple finite-state transducers generated from a weighted context-dependent rewrite rule to represent that rule. An "r" finite-state transducer is generated from the right context portion rho of the weighted context-dependent rewrite rule. An "f" finite-state transducer is generated from the rewritten portion phi of the weighted context-dependent rewrite rule. A "Replace" finite-state transducer is generated from the rewritten and replacement portions phi and psi of the weighted context-dependent rewrite rule. Finally, "l1" and "l2" finite-state transducers are generated from the left context portion lambda of the weighted context-dependent rewrite rule. The "r" and "f" finite-state transducer generators of the compiler and the transducer generating steps of the compiling method introduce the context marking symbols "<1", "<2" and ">" in the various finite-state transducers only when and where they are needed. The right context marker symbol ">" is added to the "r" finite-state transducer only immediately before each occurrence of rho . The left context markers "<1" and "<2" are added to the "f" finite-state transducer only immediately before each occurrence of phi , neglecting any occurrences of the right marker symbol ">". The "Replace", "l1" and "l2" finite-state transducers then appropriately remove the right and left context markers when replacing phi with psi , and whether lambda precedes phi in the input string.
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