mwang@watmath.UUCP (mwang) (05/30/84)
_D_E_P_A_R_T_M_E_N_T _O_F _C_O_M_P_U_T_E_R _S_C_I_E_N_C_E _U_N_I_V_E_R_S_I_T_Y _O_F _W_A_T_E_R_L_O_O _C_O_M_P_U_T_E_R _S_C_I_E_N_C_E _C_O_L_L_O_Q_U_I_U_M - Wednesday, June 6, 1984. Dr. G. Hirst of the University of Toronto will speak on ``Semantic Interpretation Against Ambiguity.'' TIME: 3:30 PM ROOM: MC 5158 ABSTRACT We describe a new approach to semantic interpretation in natural language understanding, and mechanisms for both lexical and structural disambiguation that work in concert with the semantic interpreter. Traditionally, translation from the parse tree of a sentence to a semantic representation (such as frames or procedural semantics) has always been the most ad hoc part of natural language understanding systems. However, recent advances in linguistics, most notably the system of formal semantics known as Montague seman- tics, suggest ways of putting semantic interpretation onto a cleaner and firmer foundation. Absity, the system we describe, is a Montague-inspired semantic interpreter. Like Montague formalisms, our semantics is compositional by design and is strongly typed, with semantic rules in one-to-one correspondence with the meaning-affecting rules of a Marcus parser. We have replaced the Montague semantic objects -- func- tors and truth conditions -- with elements of the frame language Frail. Absity's partial results are always well-formed Frail objects. A semantic interpreter must be able to provide feedback to the parser to help it handle structural ambiguities. In Absity, this is done by the ``Semantic Enquiry Desk,'' a process that answers the parser's questions on semantic preferences. Disambiguation of word senses and of case slots is done by a set of procedures, one per word or slot, each of which determines its correct sense in cooperation with the others. A partially disambiguated procedure's remaining possibilities are well-formed Frail objects that can be seen and used by May 30, 1984 - 2 - other processes, including the Semantic Enquiry Desk, just as a person can see many of the details of a part- ly developed ``instant'' photograph. It is from the fact that partial results are always well-formed semantic objects that the system gains much of its power. This, in turn, comes from the strict correspondence between syntax and semantics in Absity. The result is a foundation for semantic interpretation that we believe to be superior to previous approaches. Coffee and refreshments will be served at 3:00 PM. May 30, 1984