Re: getting the query from an SXP expression

(Sorry, previous reply was inadvertently not reply all).

I recall some discussion about this several years ago, and it may be possible, at least in limited cases. I’m also not aware of any other platforms which use SPARQL S-Expressions which do any de-compilation.

I had thought that this would be good for the sparql-client gem, which could take an SSE input and turn it into SPARQL Grammar, and for trivial use cases it shouldn’t be too difficult to do, but I never pursued the issue. I’d be happy for someone to look into this further and maybe create a PR, even if it is only a partial solution. To not get lost, it might be good to create an issue in https://github.com/ruby-rdf/sparql-client/issues <https://github.com/ruby-rdf/sparql-client/issues> so that we don’t loose discussions again.

Typically, the SXP is intended for optimization and execution, not to round trip back to the sparql grammar. There may be some other work on this, but I’m not aware of any. There’s quire a bit of activity in http://rdf.js.org/query-spec/c <https://github.com/rdfjs/query-spec> for that JavaScript community, and there may be some work there that could be leveraged.

In general, I would welcome more collaboration on the Ruby RDF/SPARQL gems, which have been fairly quiet for a while, other than for basic maintenance. I am planning a 3.2 release, but that will mostly be to maintain dependencies and minimum Ruby versions.

Gregg Kellogg
gregg@greggkellogg.net

> On Dec 1, 2021, at 6:35 AM, Daniel Hernandez <daniel@degu.cl> wrote:
> 
> 
> In the previous example I made a mistake it is `parse` instead of `for`
> (the question is the same).
> 
> Daniel Hernandez <daniel@degu.cl> writes:
> 
>> Hi all,
>> 
>> I am trying to get the SPARQL query of a sse expression.
>> For instance, if I have
>> 
>> exp = SPARQL::Algebra::Expression.for "(project (?x) (bgp (triple ?s ?p ?x)))"
>> 
>> then I want the string "SELECT ?x WHERE {?s ?p ?x}".
>> 
>> Thanks,
>> Daniel
>