The generated hierarchy serves as a semantic link between
the ontology for tourists and various local ontologies for
tourism information providers. On one hand, it integrates
the heterogeneous concepts in local ontologies for tourism
information providers into a single set of new concepts, as
discussed above. On the other hand, this single set of newconcepts is mapped to the concepts in the ontology for tourists,
as discussed in a later section. Thus, tourism information
at various web sites can be ultimately linked to tourists'
preferences. This approach is advantageous because by preserving the local ontologies, information about attractions
embedded in local ontologies can be effectively retrieved
according to a tourist's preferences (details are discussed in
a later section). The tourism information at various web sites
can be left intact to serve their individual purposes. The link
between the ontology for tourists and the integrated ontology
for tourism information providers is realized through the
mapping between them, as explained in the following section.