[Semediawiki-user] Proper use of categories

[Olivier D. <oli...@un...>]

Dear semantic mediawiki users,

   I am confused by what the proper use of categories should be, in the context of a semantically-enabled wiki such as mediawiki. Questions are at the end of the message.

   From what I read in [1], categories are mainly for indexing purpose and for avoiding to overwhelm the user with a huge number of pages. However, these features are also what a semantic search should do.

   Let's consider the Gustave Eiffel example [2].
   On one hand, it seems sensible to say that he is/was an instance of the Engineer and of the Architect classes. The pages of these two resources indicates that both are rdfs:subClassOf Person. Therefore, any search about engineers, architects, or engineers and architects will return a reference to Eiffel.
   On the other hand, an approach compatible with non semantically-enabled wikis would consist in stating that the Gustave Eiffel resource belongs to the categories Category:Engineer and Category:Architect, both of which being subcategories of Category:Person.

   Clearly, there is an overlap between the two approaches. The second one is not compatible with complex queries (e.g. who are the french people being both architects and engineers in the 19th century) so it is not likely to scale-up very well (e.g. why not mentionning that Eiffel's page also belongs to Category:Century19, and so on and so forth). Yet, I am not sure that we should only use the first approch exclusively and use a dummy category for all the semantically-described pages.

Q1: is there a widely accepted policy on the use of categories vs. classes that I am not aware of?
Q2: is it desirable to maintain both approaches in parallel (with the subsequent risk of inconsistencies)?
Q3: would it make sense to have the categories automatically generated from the semantic descriptions?
Q4: if answer to Q3 is yes, how do we draw the line between relevant categories and not-so-relevant categories?

Thank you,
Olivier

[1] http://meta.wikimedia.org/wiki/Category
[2] http://wiki.ontoworld.org/wiki/Gustave_Eiffel