  Administration of a Web directory and maintenance of its content and the
associated structure is a delicate and labor intensive task performed
exclusively by human domain experts. Subsequently there is an imminent risk of
a directory structures becoming unbalanced, uneven and difficult to use to all
except for a few users proficient with the particular Web directory and its
domain. These problems emphasize the need to establish two important issues: i)
generic and objective measures of Web directories structure quality, and ii)
mechanism for fully automated development of a Web directory's structure. In
this paper we demonstrate how to formally and fully integrate Web directories
with the Semantic Web vision. We propose a set of criteria for evaluation of a
Web directory's structure quality. Some criterion functions are based on
heuristics while others require the application of ontologies. We also suggest
an ontology-based algorithm for construction of Web directories. By using
ontologies to describe the semantics of Web resources and Web directories'
categories it is possible to define algorithms that can build or rearrange the
structure of a Web directory. Assessment procedures can provide feedback and
help steer the ontology-based construction process. The issues raised in the
article can be equally applied to new and existing Web directories.
