ladkin@KESTREL.ARPA.UUCP (02/25/87)
david sher said: >Note: I am not a logician but I use a lot of logic in my everyday >work which is probabilistic analysis of computer vision problems john rager replied: >When you say you use a lot of logic, do you really mean it? Recursive >function theory? Saturated model theory? Rager asks whether Sher uses infinitary methods in what seems to be a finitary context. The answer is obviously no, and I wonder why he would ask the question? Maybe he thinks that all logic is infinitary? Meanwhile, he seems to have forgotten that inference is the basis of logic, and most of us use that in one form or another. peter ladkin ladkin@kestrel.arpa
jharper@seismo.CSS.GOV@euroies.UUCP (02/27/87)
I think some useful distinction can be made between the use of _formalisms_ in AI and the use of logic(s). The function of the latter with respect to a series of inference rules and a particular domain of discourse is the characterization of truth and logical consequence. The function of the former on my own reading of AI literature concerned with NLP systems seems to merely crystallize certain _intuitions_ a researcher may have about the description and solution to a various problem. In some cases these may conform to a logical calculus, in other cases they merely appear to do so. This is quite reasonable in a research context such as AI provided one accepts that computational tractability and formal rigour are different objectives served by methodological demands. For instance, it would be impossible to build the model theory of many logics used for semantic investigations of natural language into a computational system. Yet _doing_ semantics entails the use of infinitary methodology once the model theory is based on possible worlds. Reinterpreting a semantic theory computationally is not equivalent. More fundamentally, it is the usage of the word _logic_ which is at issue. With the plethora of logical calculi it makes little sense to claim one uses _a lot of logic_ in ones work. Indeed if anyone has an uncontentious definition of modern logic please forward it.