Etapa de formulación

A lexical set is a set of lexical items (typically nouns) that occur in the same valency slot or argument position in relation to a given collocate. A lexical set, therefore, comprises both norm-compliant uses and exploitations of the norm. The ‘established norm’ cannot be rigorously defined. It is nothing but an empirical value. As Hanks puts it: “…because of the flexible, variable nature of the lexicon, even attempting a full and accurate description of the norm for any given usage may be impossible, for

1_{Emphasis has been laid on the difference between preferences and restrictions: “A restriction prevents}

or forbids you from doing something, whereas it is often the case that locutions excluded by a selectional preference are nevertheless perfectly grammatical, psychologically acceptable, and communicatively ade- quate” [56].

principled reasons: how can one define a phenomenon whose boundaries are shifting and variable?” Non-conventional verb uses are supposed to be metaphorical exploita- tions of the norms. Determining a lexical set is a performance of linguistic intuition, backed by plentiful lexical evidence.

The selectional preferences that define a lexical set are expressed in the form of non-formalized semantic labels (mnemonics). The mnemonics must apply the appro- priate degree of generalization to be able to distinguish the given meaning potential from others. Hanks discusses the example of the label Human, which is notoriously known from numerous attempts on semantic feature analysis. The label Human in- cludes some features humans share with animals (sleeping, eating, fearing, etc.) and others shared by institutions, nations, even computers (cognitive activities). The verb in question may activate only one of them. In such case the label Human would be under-specifying. The opposite extreme would be labeling the lexical sets in a way specific to the verb in question. Lexical sets do not have the same function as frame elements of FrameNet (see Section 9.6). Hanks’s solution of the semantic labeling in his own proposed ‘pattern dictionary’ is discussed below.

Lexical sets, too, should only reflect norms, not exploitations. To use one of Hanks’s examples again: one meaning potential of the English verb to urge is mainly associ- ated with horses: to urge a horse up the path etc. Finding evidence of e.g. camels being urged somewhere can result in labeling the lexical set with Steed to emphasize the im- portance of being ridden to the exact information on animal species. However, a sen- tence in which the driver urges his car somewhere, will be regarded as exploitation of the horse-ride shaped sentences. The car has adopted the steed-feature through a metaphorical transfer. The sentence acquires then the additional meaning of the driver imposing his will on his car, like a rider imposes his will on the horse, which apparently was the communicational aim of selecting the verb to urge in connection with a car. On the other hand, an exploitation can be allowed to develop into a new norm, as Hanks’s 3rd meaning potential of to urge illustrates: urging practitioners to-

wards greater involvement has the same syntactic pattern as to urge a horse somewhere. It

is now quite normal to urge people in a particular direction; much of the metaphor has already got lost by the conventionalization. Nevertheless, both complementations are regularly populated with different lexical sets. Whereas the first pattern included steeds as direct objects and adverbials of (spatial) direction, this pattern is typically populated with persons and institutions as direct objects and with adverbials of (in- tentional) direction.

In a pattern dictionary proposed by Hanks and Pustejovsky [58], two different types of labels can be used to define a lexical set. The first label, called semantic

type, belongs to an – almost – closed set of the Brandeis Semantic Ontology [137].

It renders an intrinsic attribute of the given noun at a rather general level, such as: [[Human]], [[Institution]], [[Location]], [[Body Part]], [[Vehicle]]. The semantic types can alternate. Alternations are regular choices of types within an overall pattern; e.g.:

7.2 DEFINING LEXICAL SETS

[[Human|Institution]] negotiate… [57]. The current version of the Pattern Dictionary

of English verbs, however, uses its own ontology.

The second type of label is semantic role. The semantic role renders the attribute assigned to the noun by the selection of a given verb in that particular context; i.e. ‘what implicatures does the noun obtain by being combined just with that particular verb’. For instance, the slots opened by the verb sentence are both intrinsically [[Human]], but with this particular verb, the subject [[Human]] is a Judge, whereas the object [[Hu- man]] is a Convict. Judge and Convict are semantic roles. The set of semantic roles is not closed.

More verbs can happen to have identically labelled lexical sets. However, this does not necessarily imply that the respective lexical sets are populated by the same nouns. Hanks and Jezek [57] say that lexical sets are ‘shimmering’. This is to say that “the membership of the lexical set changes from verb to verb: some words drop out while other come in, just as predicated by Wittgenstein (family resemblances). Different verbs select different prototypical members of a semantic type even if the rest of the set remains the same.”

Hanks and Jezek illustrate this phenomenon on wash and amputate. Both typically select [[Body Part]] as their direct object. One can wash any body part, but the typical collocates of wash are face|hands|hair, which one does not have amputated (at least face and hair impossibly). In such cases, not even semantic roles can help to make the lexical set more specific.

This gives an implication for building ontologies: as the lexical sets “shimmer ac- cording to what we predicate of them”, and therefore “a node in the ontology (i.e. a semantic type) is not to be thought of as an address for ‘all and only’ the lexical items that belong to that node. Rather, it is an address for lexical items that typically belong to that node. The ontology is thus best conceived, not as a rigid yes/no structure, but as a statistically based structure of shimmering lexical sets” [57].

On the contrast of to urge to its near synonym to incite Hanks shows the neces- sity to consider the lexical sets in relation to the Good-Bad axis. Incite, unlike urge, typically occurs with bad things as direct objects. When occurring with a neutral ex- pression like John incited Barry to speak to Astrid (Hanks’s example, too), the default interpretation must be that Barry’s speaking to Astrid (or speaking to Astrid in gen- eral) was something bad. This, as well as other implications and presuppositions is part of the information which a lexicon is supposed to mediate to the user, as far as this information is possible to retrieve without the risk of over-interpretation, against which Hanks himself [56] warns: “It may therefore be preferable to approach teas- ing out such implications as a matter of identifying mutual beliefs by the traditional techniques of introspection and comparison of intuition, rather than through compu- tational analysis of texts”.