Theoretical background
2.4 Temporal structure
Describing verbs by conjoining semantic primitives that constitute their core meaning is not sufficient to exhaustively capture all information they contain.
Temporal and aspectual notions play a crucial role in structuring the lexical seman-tic representation of verbs. Each verb disposes of internal temporal components that arise from the intrinsic relation between parts of the event and the time span in which they are true. For instance, the manner verb hit and the result verb break not only differ in the ways mentioned before, but also in how the events they denote take place in time.
The verbhit and most manner verbs describe events that take place without an inherent temporal endpoint, whereas the verb breakand most result verbs describe events that take place and involve an inherent temporal endpoint, namely the time when the result state comes about (Dowty,1979;Krifka,1998;Verkuyl,1972, 1993).
Verbs are separated into four major classes according to their temporal properties:
verbs ofactivity such as hit, verbs of accomplishment such as break, verbs of states such as believe and verbs of achievement such as arrive (Vendler, 1967). The
distinction between the four verb classes can be established with a number of operations which test verbs for their ability to cooccur with certain elements such as adverbial prepositional phrases or complement-taking verbs like stop (20) or adverbs like almost (21a-b).
(20) a. Accomplishment: John stopped painting the picture.
b. Activity: John stopped walking.
(21) a. Accomplishment: John almost painted a picture.
b. Achievement: John almost noticed the painting.
A more reductionist classification of verbs on the level of aspect is presented by Dowty (1972). Different aspectual properties of verbs are described in terms of a single general class of predicates (stative predicates) and a limited number of operators and connectives. Stative verbs correspond to the stative predicate BECOME in the logical structure. Verbs of other categories have logical structures that embed the stative predicate with appropriate aspectual connective and operators.
The crucial point here is the association of this predicate with the time functiont which allows to express different movements in time by adding a value (t + 1) for a forward movement in time, (t - 1) for the backward movement and (t1,t2,t3,t4,...tn) for successive moments in time. The so-called logic of change (Dowty, 1979, 76) defines the temporal content of an event with the help of the logical operators true and false. BECOME is understood as the event which is trueat t and false at t-1. For instance, the sentence the door closedimplicates two moments in time:
One with the state of the door being open t-1 and a following moment when it is replaced by a second state, namely the state of the door being closed. The class of stative verbs such as love in (22a) include a set of times t1...tn where the state of affair expressed by loveis true (22b):
(22) a. John loves Mary for three years.
b. (t:t ∈ three years) AT(t, John loves Mary)
However, the questions that arise here are: what exactly describes these and other more or less similar representations? Is it the temporal structure of the verb itself, the VP, or the whole sentence? These questions reveal themselves to be particularly important especially in the perspective of a verb lexicon aimed to reflect the natural organization of verbs as well as their general information content. That is, the temporal aspect of verbs is highly sensitive to the syntactic context in which they appear. The same verb can have two temporal structures depending on the grammatical constituents it selects. For instance, the verb draw and most accomplishment verbs have different temporal structures according to the grammatical aspect of the sentence in which they appear. In (23a) the verb draw involves the coming into existence of a circle. The progressive version of this sentence in (23b) does not involve this state of affair and there is no way to entail that a circle comes into existence.
(23) a. John drew a circle.
b. John was drawing a circle.
Additionally, as Dowty (1977) notices, draw in (24a) has a different temporal structure than in (23b) given the geometrical form of the object being drawn.
Although the two sentences are similar in not involving a accomplishment, they differ in how many moments in time the agent needs in order to draw the circle and the triangle: Obviously drawing a circle requires one action in one extended and related moment of time, whereas drawing a triangle necessitates three actions over three moments of time.
(24) a. John was drawing a circle.
b. John was drawing a triangle.
One way to neutralize these effects in representing temporal properties of verbs is to recourse to some level of generalization associated with their respective classes. This can be done by assuming the existence of two levels of temporal representation: One basic level consists of the temporal information attributed by the class to the verbs and a second level that arises as result of changes in the temporal structures of verbs due to collocational and structural factors introducing
a shifting or an extension in a way similar to meaning shifting and extension in metaphors.
A representation of temporal content of verbs that may provide a reasonable amount of generalization to be used for whole verb classes is given in Moens &
Steedman (1988). Here, the temporal structure of natural language is conveyed as an ontology which is based on contingency rather than a linear time model.
The basic notion is thenucleus. A nucleus is a structure comprising a preparatory process, a culmination and a consequent state. Aspectual types are defined according to the presence or absence of elements of the nucleus in the temporal structure of the verb. Thus, events, contrary to states, can be atomic or extended.
An atomic event is a culmination involving a final state such as (25) or a point lacking a final sate such as in (26). Furthermore, an extended event can be a culminated process, that is, a process involving a consequent state such as in (27) or a ordinary process without a consequent state (28).
(25) Harry reached the top.
(26) John hiccupped.
(27) Harry climbed to the top.
(28) Harry climbed the Mount Everest.
Since aspectual profiles are properties of sentences in a context, it is common–
as mentioned before– that external linguistic devices such as adverbs, tense etc.
influence the aspectual type of a event by adding, omitting or transforming elements in the structure of the nucleus. Such modifiers are understood as functions that
”coerce” their input (the inherent nucleus of a verb) to a target type. For instance, the progressive imposes that the aspectual type of the expression in (26) – which is atomic and punctual– to be coerced to a process by iterating the event of hiccuping (29):
(29) Sandra was hiccupping.
Similarly, the perfective coerces its input to a culmination with a consequent state in order to fulfill the adequacy condition imposed by the imperfect (28).
The importance of the temporal ontology of Moens & Steedman (1988) lays in its procedural character. A verb belongs to a basic temporal category assigned in the lexicon. It is understood as a variable undergoing a number of changes as a function of external linguistic factors. This lead to the assumption that capturing the nucleus of each event as assigned in the lexicon will provide a degree of generalization that allows to describe the temporal aspect not only of verbs but also of whole classes. Verbs belonging to the same class should share not only the same set of thematic roles, diathesis alternations and compositional semantics, but they should share the same temporal nuclei.
Summary
We presented a short overview of the theories serving VerbNet as background (for details on the concrete usage of these theories in VerbNet see chapter 9).
In particular the concept of verb classes as proposed by Fillmore (1970) and later by Levin (1993) was discussed, as well as the representation of meaning through decomposition as proposed by Jackendoff (1990a,b) and others and the representation of verbal temporal structure as proposed by Dowty (1979), Moens
& Steedman (1988) and others.
The next chapter presents related work on verb lexica for English and Arabic.