tailieunhanh - Báo cáo khoa học: "SELECTION FOR AN PARSER"

I. It is impossible to measure the merits of a grammar, seen as the component of an analyser, in absolute terms. An "ad hoc" grammar, constructed for a limited set of sentences is, w i t h o u t d o u b t , more efficient in dealing with those particular sentences than a zrammer constructed for a larger set. Therefore, t h e first rudimentary criterion, when evaluating the relation~hlp between a g r a m m a r and a set of sentences, should be t o establish whether this grammar is c a p. | STRATEGIC SELECTION FOR AN ATN SYNTACTIC PARSER Giacomo Ferrari and Oliviero Stock Istituto 41 Linguistics Computazionale - CNR Pisa Performance evaluation in the field of natural language processing Is generally recognised as being extremely complex. There are so far no pre-established criteria to deal with this problem. 1. It Is impossible to measure the merits of a grammar seen as the component of an analyser in absolute terms. An ad hoc grammar constructed for a limited set of sentences Is without doubt more efficient in dealing with those particular sentences than a grammar constructed for a larger set. Therefore the first rudimentary criterion when evaluating the relationship between a grammar and a set of sentences should be to establish whether this grammar Is capable of analysing these sentences. This is the determination of linguistic coverage and necessitates the definition of the linguistic phenomena. Independently of the linguistic theory which has been adopted to recognise these phenomena. 2. In addition to Its ability to recognise and coherently describe linguistic phenomena a grammar should be judged by Its capacity to resolve ambiguity to bypass Irrelevant errors In the text being analysed and so on. This aspect of a grammar could he regarded as its robustness 1979b 3. Examining other aspects of the problem In the analysis that we propose we will assume a grammar which Is capable of dealing with the texts which we will submit to It. Let an ATN grammar ĨI with n nodes be of this type. N will be maintained constant for the following discussion. By text we Intend a series of sentences or of utterances by one of the speakers In a dialogue. When analysing such a text once a constant N has been assumed. It is likely that in addition to the content the argument of the discourse indications will appear on the grammatical choices made by the author of the text or the speaker when expressing himself on that argument how the argument Is .