Sense enumeration and extension

The most prevalent formal theory for the lexicon is the Generative Lexicon popularized by James Pustejovsky    [95,96] and including contributions by several researchers from the European ACQUILEX project [106]. The main theme in this theory is to minimize the need for enumerating different senses of a word by providing operations for deriving most senses for a word from a basic one. This contrasts with the standard approach based on traditional lexicography (``sense-enumeration''), in which numerous distinct senses are listed for particular words. In this theory, there are four levels of representation:

Of these, the Qualia Structure is the most important with regard to sense distinctions. Instead of just a list of features or case roles, it is complex structure consisting of four parts (modeled after Aristotle's modes of explanation):

The strength of the Generative Lexicon approach lies in how the lexical types can adapt to context. This accounts for most of the reduction in the lexicon by eliminating senses which can be readily derived in context. The main generative devices for accomplishing this polymorphism are type coercion and co-compositionality. Note that these are formal devices based on Montague Semantics; this formalization clarifies the exact nature of compositional semantics (although at the expense of readability). Type coercion changes the type if an argument to that required of a predicate, provided a rule is associated with the object that effects the type shift. For instance, since ``begin'' requires an event argument, non-event arguments can only be accepted if there is a way to derive an event interpretation. In the case of ``book'', this is accomplished via the telic role of reading ( telic = read(event,agent,information,object)). Co-compositionality allows for part of the qualia structure for a verb phrase to be derived using information from the qualia structures of their arguments. This can account for the difference in ``bake a potato'' vs. ``bake a cake'' where the latter denotes a creation event rather than simply a change of state. By default, baking will refer to the change-of-state interpretation; but, since the qualia structure for ``cake'' indicates that it is the result of a bake event ( $cake{\rightarrow}agentive = bake\_act(event, agent, mass)$), the creation interpretation will result when the qualia structures are unified.