Manuscript, November 1995.
Branch expressions are implemented as a simple means of expressing structural queries over nested data contained in data exchange formats. Wildcards that range over subtrees of a data structure are introduced and a method for eliminating wildcards is described. We then demonstrate how we have embedded branch expressions into a more general system to express a richer class of queries. Finally, optimizations for migrating operations from the general system into the more efficient branch expression system are described.
See here for the paper.