Am Dienstag, den 26.05.2009, 11:29 +0100 schrieb Steve Harris: > On 26 May 2009, at 11:10, Simon Schenk wrote: > > > Am Montag, den 25.05.2009, 17:48 +0000 schrieb Seaborne, Andy: > > > >> Simon/Eric - you gave do you have examples where either MINUS or > >> EXISTS can not easily be used where EXISTS or MINUS can? > >> > >> The distinguishing example is helpful - seem to me that MINUS needs > >> a slightly artificial form to introduce ?name to be set-compatible > >> with the preceding pattern. But is this an artefact of the example > >> and is there a counter example of EXISTs having to be slightly > >> artificial? > >> > >> http://www.w3.org/2009/sparql/wiki/index.php?title=Design:Negation#Distinguish_MINUS_from_UNSAID > > > > I don't think there are cases, which can not be expressed using one of > > the forms: EXISTS can be translated into MINUS by extending the > > pattern, > > if necessary. However, MINUS really is a bit ugly in many cases. > > > >>> In addition, I still think that EXISTS without FILTER around are a > >>> bit > >>> confusing, esp. if the next clause is OPTIONAL {...}. > >> > >> I'm tending to both forms although underneath raw EXISTs because I > >> thing using iut on its own is going to be common. Internally, it > >> behaves just like a FILTER which is not moved to the end of a BGP. > > > > I think FILTER better captures the intended semantics. I am not sure, > > whether an order dependent inline form is intuitive. On the other > > hand, > > aesthetically I like it better. :) Why not completely translate it > > into > > a FILTER, including a reordering? > > Well, that means that you have to chuck in extra {}s to say what you > mean, but I'm somewhat sympathetic to the viewpoint. Having two > syntaxes that do the same thing is a bit odd. I prefer it outside > FILTER() myself, but not that strongly. Moreover, we still have !BOUND... > Won't having it inside FILTER weird the syntax a fair bit? EXISTS(...) > will have to include the whole BGP enchilada... hopefully except > FILTER and EXISTS :) You will need a nesting of FILTER / EXISTS to express double negation. Yes, there are real world use cases. ;-) Cheers, Simon -- Simon Schenk | ISWeb | Uni Koblenz http://isweb.uni-koblenz.de http://www.uni-koblenz.de/~sschenkReceived on Tuesday, 26 May 2009 11:36:22 UTC
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