- From: Kendall Clark <kendall@monkeyfist.com>
- Date: Fri, 18 Jun 2004 07:57:54 -0400
- To: public-rdf-dawg@w3.org
Folks, I'm not wedded to this wording, but I think it at least hints at an important requirement. Ideally I'd like some kind of first class syntax for a boolean query -- SELECT BOOL or SELECT ? or ASK -- but the requirement isn't as much about syntax as it is about being able to query a graph and get back TRUE or FALSE. 3.x Boolean Query It must be possible for queries to return an explicit representation of TRUE if there is at least one way that the query can be satisifed by the queried graph or an explicit representation of FALSE if there is not at least one way that the query can be satisifed by the queried graph. Additionally, I'd like a syntactic variant to distinguish this kind of query, but that's not a necessary component of the requirement as written. In response to Simon's point about variable bindings being a degenerate case of boolean result types, I can agree with that point and still want *explicit* boolean return and query types. That is, people would be perfectly free to implement Boolean Query by returning explicit FALSE or explicit TRUE based on Simon's analysis. But his analysis, at least as I understand it and these other issues, is orthogonal to how we represent boolean query results on the wire. Use cases and motivations: policy-driven RSS feed aggregators; privacy-respecting FOAF server; efficiency in the absence of streaming results; efficiency for some kinds of (mostly DL, tableau driven) DAWG processors. Interactions: I think this requirement interacts with 4.3 Non-existent triples. Which is to say 4.3 doesn't specify whether, if you query for a triple that is present in the queried graph, what is supposed to happen -- return the triple? return a binding? return TRUE? Further, I think that 3.x Boolean Query subsumes 4.3 Non-exisent Triples, but is more useful. Sometimes a boolean query would just be a query for whether a triple exists. Othertimes it will be more complex. Best, Kendall Clark
Received on Friday, 18 June 2004 07:59:59 UTC