- From: Andy Seaborne <andy.seaborne@talis.com>
- Date: Tue, 17 Nov 2009 11:35:30 +0000
- To: Steve Harris <steve.harris@garlik.com>
- CC: "public-rdf-dawg@w3.org Group" <public-rdf-dawg@w3.org>
>> This is where the fact relational algebra rename is just a rename (no >> expressions, it changes the name of a column) makes a difference here. >> We could special case the translation to the SPARQL algebra: >> >> SELECT ?x => project((?x), ....) >> SELECT (?x AS ?y) => project((?y), rename(?x as ?y) ....)) >> SELECT (?x+1 AS ?y) => project((?y), extend(?x+1 as ?y) ....)) > > But the example above was MAX(?x), so it would fall under the "extend" > semantics anyway, I think. Yes, it would fall under extend - it returns a value - I was bring up a simpler and yet nasty case :-) We do have the opportunity to define MAX itself. MAX/empty-set can be a defined to return term sparql:noValue. Not a null per se but it might work out. sparql:noValue + 0 is an error. Andy
Received on Tuesday, 17 November 2009 11:35:30 UTC