Balise : Éditeur de wikicode 2017 |
Balise : Éditeur de wikicode 2017 |
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| [[Catégorie:UNSW]] | | [[Catégorie:UNSW]] |
| == Définition == | | == Définition == |
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| | Une grammaire augmentée est ce que vous obtenez si vous prenez des règles de grammaire (généralement à partir d'une grammaire sans contexte) et leur ajoutez des informations supplémentaires, généralement sous la forme d'informations sur les fonctionnalités. |
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| == Français == | | == Français == |
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| == Anglais == | | == Anglais == |
| '''augmented grammar''' | | '''augmented grammar''' |
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| An augmented grammar is what you get if you take grammar rules (usually from a context-free grammar) and add extra information to them, usually in the form of feature information. For example, the grammar rule s → np vp can be augmented by adding feature information to indicate that say the '''agr''' feature for the vp and the np must agree:<center>s('''agr'''(?agr)) → np('''agr'''(?agr)) vp('''agr'''(?agr))</center>In Prolog, we would write something like:
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| s(P1, P3, Agr) :- np(P1, P2, Agr), vp(P2, P3, Agr).
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| Actually, this is too tough - the '''agr''' feature of a VP, in particular, is usually fairly ambiguous - for example the verb "love" (and so any VP of which it is the main verb) has '''agr'''=[1s,2s,1p,2p,3p], and we would want it to agree with the NP "we" which has '''agr'''=[1p]. This can be achieved by computing the intersection of the '''agr''' of the NP and the VP and setting the '''agr''' of the S to be this intersection, provided it is non-empty. If it is empty, then the S goal should not succeed.
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| s(P1, P3, SAgr) :-
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| np(P1, P2, NPAgr),
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| vp(P1, P2, VPAgr),
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| intersection(NPAgr, VPAgr, SAgr),
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| nonempty(SAgr).
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| where <code>intersection</code> computes the intersection of two lists (regarded as sets) and binds the third argument to this intersection, and <code>nonempty</code> succeeds if its argument is not the empty list.
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| Augmented grammar rules are also used to record '''sem''' and '''var''' features in computing logical forms, and to express the relationship between the '''sem''' and '''var''' of the left-hand side and the '''sem'''(s) and '''var'''(s) of the right-hand side. For example, for the rule vp → v (i.e. an intransitive verb), the augmented rule with '''sem''' feature could be:
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| vp('''sem'''(lambda(X, ?semv(?varv, X))), '''var'''(?varv)) →
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| v('''subcat'''(none), '''sem'''(?semv), '''var'''(?varv))
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| where '''subcat''' none indicates that this only works with an intransitive verb.
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| <small> | | <small> |
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| [http://www.cse.unsw.edu.au/~billw/nlpdict.html Source : UNWS Natural Language Processing Dictionary ] | | [http://www.cse.unsw.edu.au/~billw/nlpdict.html Source : UNWS Natural Language Processing Dictionary ] |
