Designing an Anaphora Resolution Algorithm for Route Instructions

defined as “inferences that are drawn to increase the coherence between the current
and preceding parts of a text” (Eysenck & Keane (2000), p. 528).
3.6 Here- and There-Anaphors and the SR-Algorithm
As the IBL-corpus consists of route instructions, a class of texts which contains
plenty of spatial references, this section provides suggestions how some of the
phenomena of spatial reference occurring in the IBL-corpus could be handled. As I
will show later when the evaluation of the algorithm is given, the SR-algorithm needs
further refinements. Due to time restrictions, I could not define new spatial resolution
rules which would improve the performance of the algorithm. Therefore, the spatial
reference algorithm developed within this project can only be regarded as first sketch
of an algorithm. Nonetheless, in the discussion section I will explain how the
algorithm can be improved. Since the following algorithm does not perform as
efficiently as expected, I will only briefly present the rules of the algorithm (see
Appendix 5). The first point to be considered is that all ‘here/there’s used
syntactically are excluded. This means that all ‘here/there’s which are in the subject
position are not taken into consideration. As ‘here/there’-anaphors usually refer to a
place or position specified in the utterance, their antecedent can be inferred from the
verb and from the positional or directional PP of the previous utterance. The general
approach resembles the RIAR-algorithm; the route instructions are analogously split
into units. The inputs of the algorithm are unresolved units and its outputs are
resolved units. Like the A-List in the RIAR-algorithm, the SR-algorithm constructs a
P-List in which the antecedent-position of the anaphor is presented. If the anaphors
occur in a chain, the P-List is filled after the first anaphor is resolved so that the
second and third (etc.) anaphors can be resolved to the same antecedent-position as
the first one. If the P-List is empty, it is created according to the construction rules.
Since the algorithm takes the predicative context of the ‘here/there’-anaphor into
account, it needs nine construction rules. As the P-List usually contains spatial PPs,
the construction rules determine which preposition is inserted into the P-List. This
depends on the verb and the preposition(P1) used in the previous unit. To determine
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