Unni Cathrine Eiken February 2005

When using predicate-argument structures, the definitions of argument 1 and argument 2
presupposes the existence of an underlying semantic hierarchy which defines the roles for agent
and patient. For example, argument 1 can be defined as to always representing the agent in the
sentence. An important distinction between the predicate/argument paradigm and that of
thematic roles, is that by using agent/patient as the core of the semantic representation, the
semantic classification does not focus on the predicate and its associated arguments. On the
other hand, in a predicate/argument classification, the definition of the individual arguments
does not directly consider the thematic roles. Since a semantic hierarchy has more well-defined
roles than expressible with arguments, different instances of argument 1 will not have exactly
the same semantic role, depending on the predicate they co-occur with.
For the purpose of processing the extracted structures, it is useful that the structures are in a
simplified form and also that structures that semantically convey the same information, but are
expressed in a different manner syntactically, are represented with the same structure. This is in
alignment with the doctrine of canonical form, which states the usefulness of letting linguistic
constructions which display the same meaning content give rise to the same meaning
representation (Jurafsky and Martin 2000, p. 507). By using a normalised form of
representation, such as EPAS, for the structures extracted from the text, as well as founding the
extraction method on semantic representations of the analysed texts, the generation of a
generalisable data set is achived. Active and passive constructions with equivalent semantic
meaning will be treated in the same way and will receive identical meaning representations. This
can be seen in the following example:
(3- 2)
a. Morderen drepte kvinnen.
The murderer killed the woman.
b. Kvinnen ble drept av morderen.
The woman was killed by the murderer.
c. Kvinnen ble drept.
The woman was killed.
Sentence (3-2a) and (3-2b) in essence convey the same information and only differ with
reference to verbal voice. The use of diathesis alternations of active and passive voice gives the
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