1. In a computer including a hierarchical file structure having a namespace including a pathname associated with each of a plurality of files, the pathname for each file including at least one prefix component and at least one lower-level component, an apparatus for resolving hierarchical file pathnames into representations of the files named by the paths, comprising: a memory storing a prefix cache for the hierarchical file structure which includes a representation of an upper-level portion of the namespace for the file structure, the upper-level portion of the namespace including the at least one prefix component of the pathname for each of the files; means for translating the at least one prefix pathname component for the given file into the representation of the upper-level portion of the namespace for the given file by searching the prefix cache for the at least one prefix pathname component; and means for completing resolution of the pathname for the given file when the translation succeeds by using the at least one lower-level pathname component for the given file as an input to an access pattern resolution primitive which outputs a representation of the given file.