Functional Unification Grammar: A Formalism For Machine Translation

Functional Unification Grammar provides an opportunity to encompass within one formalism and computational system the parts of machine translation systems that have usually been treated separately, natably analysis, transfer, and synthesis. Many of the advantages of this formalism come from the fact that it is monotonic allowing data structures to grow differently as different nondeterministic alternatives in a computation are pursued, but never to be modified in any way. A striking feature of this system is that it is fundamental reversible, allowing a to translate as b only if b could translate as a. I Overview A. Machine Translation A classical translating machine stands with one foot on the input text and one on the output. The input text is analyzed by the components of the machine that make up the left leg, each one feeding information into the one above it. Information is passed from component to component down the right leg to construct the output text. The components of each leg correspond to the chapters of an introductory textbook on linguistics with phonology or graphology at the bottom, then syntax, semantics, and so on. The legs join where langnages are no longer differentiated and linguistics shades off into psychology and philosophy. The higber levels are also the ones whose theoretical underpinnings are less well known and system designers therefore often tie the legs together somewhere lower down, constructing a more or less ad hoe bridge, pivot, or transfer component. We connot be sure that the classical design is the right design, or the best design, for a translating machine. But it does have several strong points. Since the structure of the components is grounded in linguistic theory, it is possible to divide each of these components into two parts: a formal description of the relevant facts about the language, and an interpreter of the formalism. The formal description is data whereas the interpreter is program. The formal description should" ideally serve the needs of synthesis and analysis indifferently. On the other hand we would expect different interpreters to be required in the two legs of the machine • We expect to be able to use identical interpreters in corresponding places in all machines of similar design because the information they embody comes from general lingusitic theory and not from particular languages. The scheme therefore has the advantage of modularity. The linguistic descriptions are independent of the leg of …