W3C home > Mailing lists > Public > public-rdf-dawg@w3.org > April to June 2011

Re: federated query question

From: Carlos Buil Aranda <cbuil@fi.upm.es>
Date: Thu, 12 May 2011 12:29:25 -0400
Message-ID: <BANLkTi=+TEm=wt-vfAVDMxdNOuopF+ipEA@mail.gmail.com>
To: Lee Feigenbaum <lee@thefigtrees.net>
Cc: SPARQL Working Group <public-rdf-dawg@w3.org>
yes, that's the point, to suggest the implementations to use some specific
order not to fail when using a variable in the endpoint address. If not, the
correct execution of the query can't be guaranteed.

Carlos

2011/5/12 Lee Feigenbaum <lee@thefigtrees.net>

> I'm reviewing the latest set of changes.
>
> In the section on boundedness (2.4) there is this note:
>
> """
> Note that this condition does not capture passing bindings between SERVICE
> pattern, e.g. in
>  { ?X :p :o SERVICE ?X { ?Y :p :o } SERVICE ?Y { ?Z :p :o } }, SERVICE ?Y
> {...} is not service-safe, since ?Y is not strongly bounded here. In order
> to capture the previous case, either SERVICE semantics have to be
> order-dependent, or the engine has to determine an implicit order of SERVICE
> calls that guarantees passing binding in the right-order:
>  { ?X :p :o SERVICE ?Y { ?Z :p :o } SERVICE ?X { ?Y :p :o } }
>
> The above query can be "emulated" with a nested SERVICE call as follows:
>
>  { ?X :p :o SERVICE ?X { ?Y :p :o SERVICE ?Y { ?Z :p :o } } }
>
> This only works if the called services support (nested) SERVICE patterns.
>
> """
>
> If I understand correctly, the intent of our current effort at including
> the notion of strongly bound is to prohibit a query that uses SERVICE like
> this. Is this correct? If so, I will change the wording to reflect this and
> to suggest that implementations might extend SERVICE by detecting an
> execution order that guarantees variables used with SERVICE are strongly
> bound.
>
> thanks,
> Lee
>
>
Received on Thursday, 12 May 2011 16:30:11 GMT

This archive was generated by hypermail 2.3.1 : Tuesday, 26 March 2013 16:15:46 GMT