  We describe an implementation in Carpenter's typed feature formalism, ALE, of
a discourse grammar of the kind proposed by Scha, Polanyi, et al. We examine
their method for resolving parallelism-dependent anaphora and show that there
is a coherent feature-structural rendition of this type of grammar which uses
the operations of priority union and generalization. We describe an
augmentation of the ALE system to encompass these operations and we show that
an appropriate choice of definition for priority union gives the desired
multiple output for examples of VP-ellipsis which exhibit a strict/sloppy
ambiguity.
