tag:blogger.com,1999:blog-3322141.post116483548724500314..comments2023-10-24T23:22:27.416+10:00Comments on More News: Different StrokesUnknownnoreply@blogger.comBlogger4125tag:blogger.com,1999:blog-3322141.post-1164843227238562112006-11-30T09:33:00.000+10:002006-11-30T09:33:00.000+10:00Paul, I'm also confused because both you and Andra...Paul, I'm also confused because both you and Andrae have written that the MINUS operator in Mulgara is the relational difference operator.<BR/><BR/>See: http://mulgara.org/pipermail/mulgara-dev/2006-October/000125.html<BR/><BR/>"* Relational-Difference - the MINUS keyword. Some of the rules in <BR/>RDFS are expressed in terms of excluding certain classes of term, and the alternatives we faced were either an O(n) filter - or a O(log n)difference."Andrewhttps://www.blogger.com/profile/00667948202593884438noreply@blogger.comtag:blogger.com,1999:blog-3322141.post-1164841450284026892006-11-30T09:04:00.000+10:002006-11-30T09:04:00.000+10:00I don't think it's substantial but there maybe som...I don't think it's substantial but there maybe something that prevents it being wrong and that is you can't actually get {{ (?x = 2, ?y = 3) }} - {{ (?y = 3) }} in JRDF from a SPARQL query. You'd get something like:<BR/>{ {(?x = 2, pred1 = 2, obj1 = 2, ?y = 3, pred2 = 3, obj2 = 3) }} - {{ (?y = 3, pred2 = 3, obj2 = 3) }}<BR/><BR/>But that still leads to the same result, AFAICT.Andrewhttps://www.blogger.com/profile/00667948202593884438noreply@blogger.comtag:blogger.com,1999:blog-3322141.post-1164841182798462882006-11-30T08:59:00.000+10:002006-11-30T08:59:00.000+10:00So the Perez et al is not compatible with set diff...So the Perez et al is not compatible with set difference. I've removed that because I found it confusing when I re-read it too.<BR/><BR/>You maybe right that the SPARQL operation matches the OWL one. That would be good.<BR/><BR/>Like I said, I've made a mistake but I'm not quite sure of the implications except the obvious one that JRDF and my thesis are complete bollocks.Andrewhttps://www.blogger.com/profile/00667948202593884438noreply@blogger.comtag:blogger.com,1999:blog-3322141.post-1164838166251926092006-11-30T08:09:00.000+10:002006-11-30T08:09:00.000+10:00I'm a little confused at your point here (and don'...I'm a little confused at your point here (and don't have time to read your original sources). You talk about the definition for "set difference" in Pérez et al, but then go on to say that, "the Pérez et al definition is much looser and isn't compatible with set difference".<BR/><BR/>At a casual reading, I'd guess that by "set difference", the relevant example you propose is the non-SPARQL one:<BR/> {{ (?x = 2, ?y = 3) }} - {{ (?y = 3) }} is {{ (?x = 2, ?y = 3) }} in relational algebra.<BR/><BR/>Right?<BR/><BR/>Of course, the difference operation in SPARQL (the \) is the one that is needed for OWL. (This is what Mulgara implements in the MINUS operator).Anonymousnoreply@blogger.com