Extracting Semantic Roles from a Model of Eventualities

The notion of semantic roles is usually at-tributed to Fillmore [8], however its history can be traced back through TesniSre [16] to Panini. Following this tradition, many researchers rec-ognize their usefulness in the description of language-- even if the

Extracting Semantic Roles from a Model of EventualitiesSylvie Ratt6 Universit6 du Qu6bec fi MontrSal / Linguistics Department C.P. 8888, Succ. "A" / Montreal, QC / H3C 3P8 e-mail: sr@info.uqam.ca The notion of semantic roles is usually attributed to Fillmore [8], however its history can be traced back through TesniSre [16] to Panini. Following this tradition, many researchers recognize their usefulness in the description of language - - even if they do not agree on their significance [7]. However, a weak or strong commitment to this notion does not elude the fact that it proves to be very difficult to settle on a finite set of labels along with their formal definitions. The dilemma resulting from this challenge is well known: to require a univocal identification by each role results in an increase in their number while to abstract their semantic content gives rise to an inconsistent set. If a finite set is possible, one has to find a proper balance between these two extremes. As a result, every flavor of roles have been used from time to time in linguistics (e.g., GB, in the spirit of Fillmore, HPSG, in the line of situation semantics), and also in AI [10, see also 4]. Between the total refusal to use those labels (as in GPSG) and the acceptance of individual roles (as in HPSG)there is a wide range of proposals on what constitute a good set o f L(inguistic)-Roles [7] and, as a consequence, on the way to differentiate between them and define them. Most of the definitions have been based on the referential properties that can be associated with each role bearer (e.g. an AGENT is a volitional animate entity). Even if this approach is necessary at one time or another, this kind of definition inevitably leads to either the "let's create another role" or the "let's abstract its definition" syndromes. Properties are not always of the static kind though. Sometimes, dynamic properties are also used (e.g. an AGENT is the perceived instigator of the action). Since one of the desired characteristic of a roles system is the power to discriminate events [5] (another "desired" property being to offer an easier selection of grammatical functions), the recognition of semantic roles should be linked to the interpretation of the event, that is to their dynamic properties. In a study on locative verbs in French, Boons [3] has convincingly shown the importance of taking into account aspectual criteria in the description of a process, suggesting that GOAL and SOURCE roles should be reinvestigated in the light of those criteria. It is our hypothesis that proliferation of roles is a natural phenomenon caused by the specialized properties required by the interpretation of a predicate within a specific semantic field: to overlook these properties yields the over-generalization already mentionned. The best way to approach the expansion/contraction dilemma is to search for the minimal relations required for a dynamic interpretation of events (in terms of their aspectual cr