Designing an Anaphora Resolution Algorithm for Route Instructions

entities referred to in the actual situation. They, therefore, have no problem finding
the right antecedent for the anaphors. This example illustrates the meaning of the
term deixis which is used by linguists in order to explain phenomena “which relate
utterances to the spatio-temporal coordinates of the act of utterance” (Lyons 1977,
p.636, quoted from Webber 1991, p. 109). The deictic anaphors refer to entities in the
spatial environment in which the speakers are situated.
Following Webber (1991) and Eckert & Strube (2000) “referents of
discourse-deictic anaphors do not exist in the discourse model unless anaphorically
referred to. For each context there are discourse entities that stand proxy for its
propositional content” (Eckert & Strube 2000, p. 59 and Webber 1991, p. 111). They
are not introduced to the discourse model by virtue of the constituent that describes
them but rather by virtue of anaphoric reference (cf. referent coercion in Eckert &
Strube 2000). Thus, deictic pronouns can have the same effect as definite noun
phrases. Both add new entities into the discourse model, such as in the following
example from Webber (1991, p. 112).
(3) I walked up the first house on my list.
I noticed that the side door was wide open.
As houses not necessarily have side doors, the listener inserts a new entity for ‘the
side door of this house’ into the discourse model. This process is called
accommodation because “the use of a singular definite is felt to presuppose that there
is already a unique entity in the context with the given description” (Webber 1991,
p.112).
Items in the discourse model which are mentioned in the previous discourse
are called salient, whereas the most salient entities which attract the attention of the
discourse participant at any point in the discourse are called focused entities. Various
theories define salience and focus with respect to different criteria, but it is generally
agreed that items which occur as noun phrases in the sentence are more salient than
other items. Due to the occurrence of long-distance anaphora, discourse entities
evoked by noun phrases remain in the discourse model for the duration of the
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