- From: Chimezie Ogbuji <ogbujic@ccf.org>
- Date: Tue, 11 Aug 2009 09:40:48 -0400
- To: "Seaborne, Andy" <andy.seaborne@hp.com>, "SPARQL Working Group" <public-rdf-dawg@w3.org>
Hey Andy On 8/10/09 9:10 AM, "Seaborne, Andy" <andy.seaborne@hp.com> wrote: >> http://www.w3.org/2009/sparql/wiki/Design:Aggregate > Hi Chime, > Yes - including LaTeX is hard. I think you can cut-and-paste the symbols into > the wiki text because it's all UTF-8 HTML but that's a bit fragile and only > marginally better. Okay, thanks. I'll give that a try > I took tried to write out some formal definitions to check my understanding: > is this the sort of thing you had in mind? > > > Single valued function: returns a solution projected down to named variables > only: > key(varlist, mu) = { (v,x) | (v,x) in mu, v in varlist } > > and the set of all keys: > key(varlist, Omega) = { k | mu in Omeag, k=key(varlist,mu) } > > The partition of the multiset Omega is: > Partition(varlist, Omega) = { (k,mu) | mu in Omega, k=key(varlist, mu) } Yes, this needs to return a set from the multiset and varlist in order to ensure uniqueness of the partitions. > Let agg(VarList,SubOmega) be the aggregation function run on a multiset of > solutions taking variables VarList > > Aggregation(VarList, FuncAndVars, Omega, Mu) = > { merge(k, (Vout, agg(Vin,X)) | (k, X) in Partition(varlist, Omega), > FuncAndVars=(f, Vin, Vout), agg in set f } I believe we are on the same page. > Aside: we may need to restrict variable Vout so it does not clash with the > key. Yes. > One last point: do we want GROUP BY expressions, not just variables? In think > we do; does create some issues about the projected down variables that are > arguments to the partitioning expression. > Some SQL systems put a random > selection (AKAK first found?) but I prefer to not include the variables of an > expression at all so as to get ehy same results each time. > > Andy Good question, I don't know off head (will need to chew on that). -- Chimezie =================================== 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 Tuesday, 11 August 2009 13:41:50 UTC