They Say It's A New Sort Of Engine: But The SUMP's Still There

I shall lump the specific semantic formalisms currently touted together as manifestations of logicism, because the issue is whether the logicist approach to language processing is the right one, not whether one particular formalism is better than another. The [ogicist model of language processing is essentially as follows. We use a phrase structure grammar, heavily laced with features, for syntactic parsing; in analysis syntactic processing drives semantic interpretation strictly compositionally, to build a logical form representing the literal meaning of a sentence. This logical form is further processed, both in discourse operations of a larger scale linguistic character, as in (some) pronoun resolution, and, more importantly, in inference on global and local world knowledge, to obtain a filled-out utterance interpretation. Logical form plays a key role, motivated as much by the need for reasoning to complete interpretation as by the need to supply an appropriate input to further reactive problem solving. The use of a logical form to represent the meaning of an input naturally fits the use of a logical formalism to characterise general and specific knowledge of the world to which a discourse refers and in which it occurs. Whether the logicist position is psychologically plausible is not an issue here: it can be adopted as a base for language processing without a commitment to, say, FOPC as a vehicle for human thought, and indeed can be adopted in a psychologically implausible form, for example with complete syntactic processing followed by semantic processing. The fact that a good deal of development work is being done using a case frame approach is no problem for the logicist either: case frames are either an alternative notation or can only work for the discourse of very restricted applications. The logicists' problems are those of getting an expressive and tractable enough logic: what sort of logic is powerful enough to capture linguistic constructs, characterise the world, and support common-sense reasoning; and is this logic computationally practical? Determining and representing the knowledge required for a particular system application is not necessarily more of a problem for the logicist than for anyone else. The threat to the logicist's moral, or at least mental, purity is Whether a logic which will do the job is really a logic at all. If the world is heterogeneous, our thinking sloppy, and our language uncertain, whatever closely reflects these may be barely worthy of the label "logic". This is not to rake up the old semantic nets versus predicate logic controversy, or its analogues. We may have a formalism with axioms, rules of inference, and so forth which is quite kosher as far as the manifest criteria for logics go, but which is a logic only in the letter, not the spirit. This is because, to do its job, it has got to absorb