Unni Cathrine Eiken February 2005

(2- 8)
The sergeant’s suspect hurt himself.
Hellan (1988) suggests that the principles of standard Government and Binding theory are
primarily based on English and that they cover “a very limited subpart if what constitutes a
possible anaphoric system” (Hellan 1988, preface). He proposes several additional principles,
maybe most notably the Command Principle in which, among other statements pertaining to the
command relation, it is stated that also relations within hierarchies of thematic roles can stand in
a command relation to an anaphor.
2.1.2 Computational approaches to anaphora resolution
Automated anaphora resolution systems basically have to perform three separate tasks (Mitkov
2003):
• identify the anaphors to be resolved
• locate the candidates for antecedents
• select the antecedent from the candidate list
Different computational approaches apply different resolution factors and knowledge sources.
The process of resolving the antecedent is based on several resolution factors, which in turn
draw into account quite different sources of background knowledge. Using morphological
knowledge may be the simplest approach; gender and/or number is compared and candidates are
discounted if their gender/number does not fit that of the anaphor. Syntactic knowledge is used
to identify syntactic parallelism; the antecedent is often found in a similar syntactic position as
the anaphor. In many cases, the correct antecedent cannot be identified without the help of
semantic information. Selectional constraints is one example of semantic knowledge that can be
used to narrow down the list of candidates for the antecedent. Repeated mention of an entity in
the preceding text passage to the anaphor may indicate that this entity has a higher degree of
salience in the discourse and that it therefore is a likely antecedent for a following anaphor
(Jurafsky and Martin 2000, p. 682). Using morphological, lexical, syntactic, semantic and
salience criteria as background knowledge does not immediately suggest the most likely
candidate, but rather acts as filters to eliminate unsuitable candidates (Mitkov 2003, p. 271).
Mitkov (2003, p. 272) states that for some examples “the crucial and most reliable factor in
deciding on the antecedent” is real-world knowledge. Even the most exquisite anaphora
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