Syntactic frames, as descriptions of the subcategorisation structure of a verb, are present in all the approaches to lexical specification which have been examined. Abstracting away from theory- and system-specific coding protocols, we may characterise a frame as a generalisation over different syntactic contexts required by a verb and that are associated with the same syntactic behaviour. In our recommendations, and also to fulfil the requirement of being open, the precise criteria to decide when to generalise into one frame and when to split information over different frames are not fully given and some choices must still therefore be made by the user when filling out the proposed Frame description.
Frames can be defined for each verb type by providing:
A frame represents synthetically a set of possible syntactic structures associated with the verb. In a frame, the combinatorial realisations of slots are supposed to yield possible surface instantiations of the frame. In other words, for some syntactic structure associated with a verb, each slot of the verb frame will either have some realisation, or it will have none if the slot can be optionally left unrealised. Constraints on realisation give criteria to split frames in some cases. Slots are described as independent of each other from the point of view of their realisation, but they are linked with constraints on linear precedence, as well as with control relations.
The synthesis of these different basic notions and their relations is made through the notion of syntactic frame, which can be represented as in figure 4.1.
Figure 4.1: Representation of FRAME
The different descriptive elements that can be shared by other descriptive elements have an attribute identifier (id), that is, a unique key, that allows other elements to point to them by means of this id. Some descriptive elements (e.g. slot) can be present ``0, 1 or n times'' (conventionally expressed by `*'). Some descriptive elements (e.g. realisation) can be present ``1 or n times'' (conventionally expressed by `+').