Designing an Anaphora Resolution Algorithm for Route Instructions

in the following example refers to two different roads, since the second road is
specified by a prepositional phrase. Moreover, due to inference processes we know
that after ‘following one road’, you ‘take another one’.
1) follow on the road
and then take the road on your right
But the following example shows that different linguistic input might refer to the
same entity.
2) take the second road on your right
and follow it until you reach the museum
Thus, in order to resolve anaphors occurring in route instructions, inference methods
are needed. But let us first look what is meant by anaphoric reference in general.
2.2 Discourse and Anaphoric Reference
Before focussing on anaphora resolution, I should like to elucidate some theoretical
concepts and definitions. Any kind of communication introduces information about
objects, situations, events, facts etc. into the addressee’s mental model (discourse
model). It is part of the context that participants use in understanding the meaning of
a text. The discourse model contains representations of the entities that have been
referred to in the ongoing discourse (discourse entities or discourse referents) and it
also stores attributes of the discourse entities and information about the relationships
in which the entities participate. The meaning of a term may depend on the previous
discourse and it may also be affected by the spatio-temporal context which the
discourse participants share and of which they are mutually aware. Reference to any
entity that has been previously introduced into the discourse is called anaphora.
Anaphora resolution is defined as a two-phase process: firstly constructing a
discourse model which stores any kind of information from the ongoing discourse;
i.e. identifying what is available in a text for anaphoric reference; and secondly
merging the anaphor with its referent, i.e. constraining the set of accessible candidates
so that only one choice for the given anaphor is left. Most of the existing anaphora
resolution algorithms only generate discourse entities for the referents of noun
phrases. However, discourse entities represent any kind of participation of a particular
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