Unlike the rst three concepts, the derivation of
sub-concepts for `provided activities' is challenging.
Activities are typically organized into hierarchical structures,
but different tourism information providers may group them
differently. The same sub-concept name may be assigned
to different categories and at different levels by different
providers. The number of categorization levels may differ as
well. Two steps are necessary to identify the sub-concepts
for the `provided activities.' The rst is to identify the
sub-concepts in each local ontology. The second is to
organize these sub-concepts into a single multi-level
hierarchy. These concepts can then be consistently represented and understood. In this paper, the FCA approach is
used to perform these two tasks, as described below.