Kelly Jones wrote: > SQL has views, spreadsheets have equations. Does RDF have the concept > of a "calculated value"?
Well, this is a weird question. RDF *the model* doesn't and, IMO, shouldn't. RDF *the ecosystem* sorta does but it's mostly up to you at this point. > Example: > > "Bob's Gym" number_of_male_members 100 > "Bob's Gym" number_of_female_members 150 > > It of course follows (assuming no hermaphrodites/aliens/etc): > > "Bob's Gym" total_members 250 > > but it seems silly and redundant to have to say that. If your RDF > model has several gyms, each will have an unnecessary extra line of data. > > Does RDF have the concept of: > > $x total_members $x.number_of_male_members+$x.number_of_female_members > > meaning: "for any $x in this RDF model, the total_members of $x is the > sum of number_of_male_members of $x and the number_of_female_members > of $x". In a nice world, your triple store would be smart enough to understand where query hot-spots are and 'precalculate' and cache emerged views for you. In a more normal world, your triple store would allow you to have operators (reasoners, rule engines, whatever) that allow you to generate new statements based on existing one, and these could be used to emerge such views. (I'm working on such a system right now) > A more complex example could involve grouping or joins. For example: > the population of a state is the sum of the populations of all cities > in that state [this isn't really true since some people live in > unincorporated areas-- just an example] That said, nothing prevents you from 'emerging' such views yourself right now. Perform the query and resave the results into the triple store. -- Stefano Mazzocchi Digital Libraries Research Group Research Scientist Massachusetts Institute of Technology E25-131, 77 Massachusetts Ave skype: stefanomazzocchi Cambridge, MA 02139-4307, USA email: stefanom at mit . edu ------------------------------------------------------------------- _______________________________________________ General mailing list [email protected] http://simile.mit.edu/mailman/listinfo/general
