- From: Eric Prud'hommeaux <eric@w3.org>
- Date: Wed, 14 Jun 2006 17:58:29 +0200
- To: Jorge Adrián Pérez Rojas <jperez@ing.puc.cl>
- Cc: public-rdf-dawg-comments@w3.org
On Tue, Jun 13, 2006 at 11:12:28AM -0400, Jorge Adrián Pérez Rojas wrote: > Eric Prud'hommeaux wrote: > > On Mon, Jun 12, 2006 at 05:52:52PM -0400, Jorge Pérez wrote: > >> Hi Eric, > >> > >> I've been following the development of SPARQL for a couple of months and > >> I've a comment about your last mail on public-rdf-dawg (I've no access > >> to > >> this list so I'm writing only to you). > >> > >> You say that a query like > >> > >> ... > >> WHERE { > >> ?a dc10:title "thing" . > >> OPTIONAL { ?a dc10:creator ?name } > >> ?a cc:license ?license . > >> OPTIONAL { ?a dc11:creator ?c . > >> ?c rdf:value ?name } > >> } > >> > >> must be evaluated as two patterns with OPTIONALs in them. What I > >> understand from what yo say is that we have a group graph pattern with > >> two > >> OPTIONAL patterns inside: > >> > >> ?a dc10:title "thing" . > >> OPTIONAL { ?a dc10:creator ?name } > >> > >> and > >> > >> ?a cc:license ?license . > >> OPTIONAL { ?a dc11:creator ?c . > >> ?c rdf:value ?name } > >> > >> is that correct? If this is the case the spec says that the solutions > >> are > >> the ones that are solution simultaneously to both patterns, > > > > I disagree with the "simultaneously" part. That is, I think the "any" in > > [[ > > There is no implied order of graph patterns within a Group Graph > > Pattern. Any solution for the group graph pattern that can satisfy all > > the graph patterns in the group is valid, independently of the order > > that may be implied by the lexical order of the graph patterns in the > > group. > > ]] > > means that it's a union of all of the possible interpretations. > > Im ok with the *any* part, but the *simultaneously* part in my argument > refeer to the **all** part in > [[ > There is no implied order of graph patterns within a Group Graph > Pattern. Any solution for the group graph pattern that can satisfy **all** > the graph patterns in the group is valid, independently of the order > that may be implied by the lexical order of the graph patterns in the > group. > ]] > > so, from my point of view, the mapping > > | ?name | ?c | > +--------------+-------+ > | "John Smith" | | > > is not a solution because it do not satisfy **all** the graph patterns in > the group (it do not satisfy the second OPTIONAL graph patter in the > group). Interesting. That's certainly a valid interpretation of "all". My interpretation had been that a solution satisfies all of the constraints when evaluated in any given order. Yours appears to be <-+ that a solutions satisfies all the constrains when evaluated in all | possible orders. | | There are some folks who are working on clarifying the formal | semantics right now; I'll ask them to look at this. Hey AndyS, PatH, | FredZ, look at this:--------------------------------------------------+ > Acording to your argument the query > > SELECT ?name > WHERE > { > { ?a dc10:creator ?name }. > { ?b rdf:value ?name } > } > > will also be a union of all of the possible interpretations, and then will > have as solution the mappings > > | ?name | > +--------------+ > | "John Smith" | > | "Joe Bloggs" | > > is that correct? > If the **all** is changed for **any of** in the spec I would read the spec > in the same way as you do. > > I understand the center of your argument now, thanks for the clarification. > > - jorge > > > > >> so I think > >> the > >> above query agaisnt the following data > >> > >> :a dc10:title "thing" . > >> :a dc10:creator "John Smith" . > >> :a cc:license "steal this book" > >> :a dc:11:creator _:jb . > >> _:jb rdf:value "Joe Bloggs" . > >> > >> has empty solution. For example, the mapping > >> > >> | ?name | ?c | > >> +--------------+-------+ > >> | "John Smith" | | > >> > >> could not be a solution because although it is a solution for the first > >> pattern it is not a solution for the second pattern. Similarly the > >> mapping > >> > >> | ?name | ?c | > >> +--------------+-------+ > >> | "Joe Bloggs" | _:jb1 | > >> > >> is not a solution because it is not a solution for the first pattern. Am > >> I > >> misreading something about your arguments? > >> > >> Greetings, > >> Jorge Perez > > > > -- > > -eric > > > > home-office: +1.617.395.1213 (usually 900-2300 CET) > > cell: +81.90.6533.3882 > > > > (eric@w3.org) > > Feel free to forward this message to any list for any purpose other than > > email address distribution. > > > > > -- -eric home-office: +1.617.395.1213 (usually 900-2300 CET) cell: +81.90.6533.3882 (eric@w3.org) Feel free to forward this message to any list for any purpose other than email address distribution.
Received on Wednesday, 14 June 2006 15:56:56 UTC