- From: Chimezie Ogbuji <ogbujic@ccf.org>
- Date: Fri, 13 Mar 2009 20:53:22 -0400
- To: "Lee Feigenbaum" <lee@thefigtrees.net>
- cc: "Seaborne, Andy" <andy.seaborne@hp.com>, "SPARQL Working Group" <public-rdf-dawg@w3.org>
Originally, I was concerned that arbitrarily-nested sub-selects might introduce some non-linear recursion that using ASK as FILTER expressions does not. So, the limitations I had in mind were syntactic and ensured the recursion in sub-selects are not of the more complex kind. However, the scoping effect of group graph patterns used with sub-selects seems to ensure that computations within a sub-select are local to the group graph pattern with the exception of the solutions returned: SELECT ... { { SELECT ... { ... } } } I'm not so sure about whether the proposed assignment syntax provides the same (or similar) guarantees. -- Chimezie On 3/12/09 9:21 PM, "Lee Feigenbaum" <lee@thefigtrees.net> wrote: > Chimezie Ogbuji wrote: >> On 3/12/09 9:14 AM, "Seaborne, Andy" <andy.seaborne@hp.com> wrote: >>> As for implementation, putting subs-selects was not hard when I added the >>> functionality in ARQ and I didn't have an existing DB engine to pull >>> existing >>> features from. I don't think it was luck that other designs decisions had >>> set >>> things up, more it was a natural step. Other opinions may differ. >>> What is hard, as had been pointed out, is optimization, but that is not to >>> be >>> specified. >> >> I don't think I agree that optimization and implementation effort (which is >> a direct consequence of the complexity introduced by more expressive query >> forms such as sub-selects) should *not* be a factor. In fact, it is mostly >> my concern in this regard that motivates me to suggest that we consider a >> spectrum of sub-select features to include. > > Chime, I was intrigued by your suggestion regarding a limited form of > sub-select on the teleconference, but admit that I couldn't immediately > see what that would look like. Do you have a concrete proposal for how > this might work? (just a sketch would be helpful!) > > thanks, > Lee > =================================== P Please consider the environment before printing this e-mail Cleveland Clinic is ranked one of the top hospitals in America by U.S. News & World Report (2008). Visit us online at http://www.clevelandclinic.org for a complete listing of our services, staff and locations. Confidentiality Note: This message is intended for use only by the individual or entity to which it is addressed and may contain information that is privileged, confidential, and exempt from disclosure under applicable law. If the reader of this message is not the intended recipient or the employee or agent responsible for delivering the message to the intended recipient, you are hereby notified that any dissemination, distribution or copying of this communication is strictly prohibited. If you have received this communication in error, please contact the sender immediately and destroy the material in its entirety, whether electronic or hard copy. Thank you.
Received on Saturday, 14 March 2009 00:54:19 UTC