- From: Marcelo Arenas <marcelo.arenas1@gmail.com>
- Date: Wed, 3 Mar 2010 14:51:07 -0300
- To: Juan Sequeda <juanfederico@gmail.com>
- Cc: Lee Feigenbaum <lee@thefigtrees.net>, RDB2RDF Working Group <public-rdb2rdf-wg@w3.org>
Hi Juan, On Wed, Mar 3, 2010 at 12:26 PM, Juan Sequeda <juanfederico@gmail.com> wrote: >> >> """ >> Ahmed: ericP, can you please ask Ivan also about SPARQL >> ... about the max expressivity of SPARQL because we don't want to have a >> mapping language that supports more expressivity than SPARQL >> """ > > The paper by Angles and Gutierrez [1] states that SPARQL and non-recursive > safe Datalog with negation have equivalent expressive power, and therefore > the expressiveness of SPARQL is equivalent to relational algebra. > We have represented the translation of sql schema to rdf schema/ owl in FOL > and Datalog [2]. > Marcelo, correct me if I'm wrong... if we represent our mapping language in > Datalog, then we don't have to worry if it is more expressive than SPARQL... Yes, if you use non-recursive Datalog with safe negation then you don't have to worry if it is more expressive than SPARQL. > AND.. we don't have to worry about the semantics of the language. The only > thing we would have to work on is the syntax. This is a nice feature of the Datalog approach, you don't have to worry about the semantics of the language as the semantics of Datalog is well defined. Does the mapping language include some built-in predicates (like order)? If this is the case, then some care has to be taken when defining the semantics of Datalog and comparing the expressiveness of this language with that of SPARQL. Best regards, Marcelo
Received on Wednesday, 3 March 2010 17:51:40 UTC