Re: getting the query from an SXP expression

Thank you Gregg that looks really awesome!

On Wed, Jan 19, 2022, 22:50 Gregg Kellogg <gregg@greggkellogg.net> wrote:

> For those following the SPARQL re-serialization issue: While there was
> initial support un release 3.2.0 of the sparql gem, this was limited to
> fairly trivieal use cases. In 3.2.1 [1][2] there’s fairly comprehensive
> support for all but the most complicated SPARQL expressions with most
> test-suite inputs now re-serializable. This includes SPARQL-star tests.
>
> Gregg Kellogg
> gregg@greggkellogg.net
>
> [1] https://github.com/ruby-rdf/sparql/releases/tag/3.2.1
> [2] https://rubygems.org/gems/sparql
>
> On Dec 27, 2021, at 1:33 PM, Gregg Kellogg <gregg@greggkellogg.net> wrote:
>
> Support for #to_sparql on Operator, and other classes, is no implemented
> on the develop branch, and will be released shortly in a 3.1.0 release.
>
> It should work for simple queries, but will likely run into issues for
> things that get too complicated. It does include re-serializing any prefix
> or base IRI declarations and using to shorten embedded IRIs, as well as for
> updates as well as queries.
>
> From Daniel’s original example:
>
> query = SPARQL.parse 'SELECT ?s WHERE { ?s ?p ?o }’
> query.to_sparql #=> "SELECT ?s\nWHERE {\n?s ?p ?o .\n}\n”
>
> There’s really no attempt at trying to make whitespace pretty, I’m afraid.
>
> See https://github.com/ruby-rdf/sparql/issues/38
>
> Thanks to Aymeric and Andy for suggestions, although the approach taken is
> somewhat different.
>
> Gregg Kellogg
> gregg@greggkellogg.net
>
> On Dec 2, 2021, at 3:05 AM, Daniel Hernandez <daniel@degu.cl> wrote:
>
>
> Thank you for your answer.  I think now I understand better the role
> that play SPARQL::Grammar, SPARQL::Algebra, and SPARQL::Client (please
> fix me if I am wrong).  The first two allow for creating instances of an
> algebraic expression from a string (using either the SPARQL or the SSE
> grammars), and can be translated to SSE.  The last provides a DSL to
> define queries, and does not care about the SPARQL algebra.
>
> Gregg, I am going to implement the hypothetical method inside my app,
> for some few cases, and then I am going to share the code to see if this
> is useful for the general implementation.
>
> Daniel Hernández
>
> Gregg Kellogg <gregg@greggkellogg.net> writes:
>
> The approach Jena takes probably makes it better to have such a mechanism
> be part of the core sparql gem, not restricted to sparq-client. I created
> an issue for it in the sparql repo [1].
>
> A hypothetical SPARQL::Algebra::Operator#to_sparql method might method
> that could be used to do this.
>
> Gregg Kellogg
> gregg@greggkellogg.net
>
> [1] https://github.com/ruby-rdf/sparql/issues/38 <
> https://github.com/ruby-rdf/sparql/issues/38>
>
> On Dec 1, 2021, at 1:45 PM, Gregg Kellogg <gregg@greggkellogg.com> wrote:
>
> Thanks Andy, that’s what I was looking for. Could be ported to Ruby
> reasonably.
>
> Gregg Kellogg
>
> SPARQL::Algebra::Operator>> Sent from my iPhone
>
>
> On Dec 1, 2021, at 1:13 PM, Andy Seaborne <andy@seaborne.org> wrote:
>
> 
>
> On 01/12/2021 20:30, Gregg Kellogg wrote:
> (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.
>
>
> Jena tries to - it's quite pragmatic:
>
>
> https://github.com/apache/jena/blob/main/jena-arq/src/main/java/org/apache/jena/sparql/algebra/OpAsQuery.java
>
>  Andy
>
> 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/ <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 <mailto:gregg@greggkellogg.net
> <gregg@greggkellogg.net>>
>
> On Dec 1, 2021, at 6:35 AM, Daniel Hernandez <daniel@degu.cl <
> mailto:daniel@degu.cl <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 <mailto:daniel@degu.cl <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
>
>
>
>
>
>
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