Predicate-Argument Structure

In natural language sentences, events or relations are frequently expressed by verbs, but in the case of support verb constructions they are expressed by nominal predicates. Predicate-argument relations are labeled either with grammatical functions (subject, object, etc.), thematic roles (theme, agent, patient) or some other scheme (ARG1, ARG2, ARG3), depending on the theoretical framework. Predicate-argument structure establishes which items are predicates and which items are arguments. Independently of the framework, predicate-argument structure is used to describe levels of representation that neutralize some of the different ways the same ideas can be expressed. Certain syntactic operations, such as passivization, can change the syntactic argument valency, but the semantic arguments remain unchangeable. For example, the same predicate- argument representation may be able to represent both the active and passive. In the

SUPPORT VERB CONSTRUCTIONS

69 sentence the doctors operated on John, the arguments are: ARG0=doctors, and ARG1=John, while in the sentence John was operated on, the only argument is: ARG0=John. Even though there was a change in the number of syntactic arguments and the grammatical function "subject" changed (doctors in the active and John in the passive), the semantic argument did not change. In both sentences John is the patient, independently of its grammatical function. If the syntactic argument is left unexpressed, as in the case of agentless passives, the semantic argument is not expressed.

Much work has been done to identify underlying argument structures in English, but less in other languages. Most of it is related to the lexicon because much of this information is specific to individual words, such as verbs or to small classes of words, such as support verb constructions. Some resources already consider these linguistic relationships. For example, PropBank [Palmer et al., 2005] corpus includes predicate- argument structure and applies it to the Penn Treebank [Santorini, 1990] [Marcus et al., 1993] as relation between nodes on the trees using predefined argument frames of verbs [Kingsbury et al., 2002]. Also, some works in the biomedical field discuss the nature of predicate-argument structures for event or relation information extraction purposes. Predicate-argument structure seems to be a useful intermediate structure for information extraction in domains such as molecular biology [Tateisi et al., 2004] and is suitable for representing aspects of the semantics of biomedical verbs [Cohen & Hunter, 2006] [Cohen et al., 2008]. Nevertheless, the analysis of verb phrases is not sufficient to establish the predicate-argument structure, because events and relations can be and often are expressed in nominal phrases or in verbal phrases with predicate nominals. So, it is important to analyze phrases involving non-verbal predicates. As pointed out earlier, works such as [Meyers et al., 2004a]; [Meyers et al., 2004b] have been focusing on predicate nominals, including the analysis and formalization of nominalizations, which occur frequently in support verb constructions. NOMLEX is a dictionary of English nominalizations that describes the allowed complements for a nominalization and relates the nominal complements to the arguments of the corresponding verb. Support verbs share arguments with the nominalizations, so the relationship between the two is captured at the dictionary level.

As demonstrated by [Mel’čuk, 1988] and [Mel’čuk, 1996], different support verbs have different argument-sharing properties. For example, in English the support verb

SUPPORT VERB CONSTRUCTIONS

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construction to have a visit is different from the support verb construction to pay a visit because the subject of the support verb to have is the object of visit, but the subject of the support verb to pay is the subject of visit. In John had a visit someone visits John, whereas in John paid a visit, John visits someone. Mel’čuk lists three lexical functions that apply specifically to support verb constructions containing nominalizations: Operi,Funci,

Labori,j. In this work we are only handling the cases where the predicate noun is the direct

object of the support verb subject (Operi), which are by large the most frequent ones.

However, the analysis becomes more complex when the same support verb has two distinct predicate-argument structures. This is the case of the Portuguese support verb fazer (to do) that appears with a double function in many support verb constructions, especially biomedical-related support verb constructions. For example, the Portuguese support verb construction fazer uma amputação (Ŧ to make an amputation) is ambiguous as far as its semantic role is concerned. It can mean either that someone is doing it or that someone is having it done. So, depending on the arguments of the predicate in one reading or another, the expression can mean to perform an amputation on someone paraphraseable by amputar alguém (amputate someone’s + body part) or to have an amputation paraphraseable by ser amputado (body part + to be amputated). In the first reading, the following arguments are involved: (1) ARG0, corresponding to "who", (2) ARG1 corresponding to "what", (3) ARG2 corresponding to "of what" and (4) ARG3 corresponding to "whom". In the second reading, the arguments involved are: (1) ARG0, corresponding to "what", (2) ARG2 corresponding to "of whom", (3) and argument ARG3 corresponds to "what". If the argument ARG0 or subject of the support verb is an agent, such as a doctor or another health care practitioner responsible for the procedure amputation, the construction means to perform an amputation on or to amputate on. On the other hand, if the argument ARG0 of the support verb is a patient, the construction means to have/undergo an amputation or (body part + to be amputated).