This must be an old version of ARQ you are using, assign is the precursor
to the extend algebra operator which generally corresponds to the BIND
keyword in SPARQL 1.1 (http://www.w3.org/TR/sparql11-query/#bind)
This is most definitely pre-Apache era ARQ since it still has arq.jar and
arq-extra.jar
I would strongly recommend either writing your own library to do this or
forking the Mediation library and porting it to run against the current
ARQ.
Rob
On 3/22/13 10:01 AM, "Diogo FC Patrao" <djogopat...@gmail.com> wrote:
>Hello Rob, Claude
>
>Thanks for your answers. I'm in a bit of a problem, because I'm using a
>library called Mediation [1], which in fact does the Transformation.
>
>However this library relies on a earlier version of Jena, and it won't
>work
>with the last version. And this earlier version doesn`t provide
>Syntax.syntaxSPARQL_11, so I can't issue the queries anyway =/
>
>I'm rendering back the query, implementing the OpAsQuery missing methods.
>However I got another doubt, check the query below:
>
>select ?p count( ?b ) { ?p a <http://marafo.com#Paciente>. ?a <
>http://marafo.com#tem> ?b. LET ( ?marafo := ?b+1 ) } group by ?p
>
>
>The generated algebra is:
>
>(project (?p ?.1)
>
> (assign ((?.1 ?.0))
>
> (group (?p) ((?.0 (count ?b)))
>
> (bgp
>
> (triple ?p <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <
>http://marafo.com#Paciente>)
>
> (triple ?a <http://marafo.com#tem> ?b)
>
> ))))
>
>
>I didn't get why is there this "(assign (?.1 ?.0) ) " thing... can someone
>enlighten me?
>
>
>Thanks again!
>
>
>
>[1] https://github.com/correndo/mediation
>
>--
>diogo patrão
>
>
>
>
>On Thu, Mar 21, 2013 at 3:52 AM, Claude Warren <cla...@xenei.com> wrote:
>
>> Diogo,
>>
>> When I implemented similar functionality for Granatum I implemented a
>> QueryEngine by extending QueryEngineMain and overriding modifyOp(Op). I
>> was able to make extensive modifications to the query (including
>>inserting
>> service calls). It is not trivial but it is doable. I assume you are
>> trying to do something like FedX or DARQ.
>>
>> Claude
>>
>> On Thu, Mar 21, 2013 at 1:45 AM, Diogo FC Patrao <djogopat...@gmail.com
>> >wrote:
>>
>> > Hello
>> >
>> > I'm working on a sparql query "expander", that is, it add triples and
>> > filters to a query in order to emulate some inference (say you have A
>>->
>> B
>> > AND C, and a query SELECT * { ?s rdfs:type A }, it would return
>>SELECT *
>> {
>> > ?s rdfs:type B. ?s rdfs:type C}).
>> >
>> > I'm manipulating sparql queries on the algebra level (using
>>Transformer),
>> > and then I'm returning it as a query, using OpAsQuery. However, not
>>all
>> > algebras can be translated back, specifically, those using SERVICE.
>> >
>> > I found this link [1] and decided to execute the algebra directly.
>> However,
>> > the example code in the link has two issues (for what I want):
>> >
>> > a) it returns a QueryIterator, not a Resultset.
>> >
>> > b) it`s not clear how I specify a remote sparql endpoint.
>> >
>> > c) I feel like I would have to rewrite (or clone) some code
>> >
>> > So I thought that maybe the best thing for me would be to run my
>> > transformation in the middle of the query execution pipeline.
>> >
>> > Is there a way to accomplish that? If not, what you feel as the best
>>way
>> > out (including implementing all stuff missing on OpAsQuery)?
>> >
>> > Thanks in advance!
>> >
>> >
>> >
>> > [1]:
>> >
>> >
>>
>>http://mail-archives.apache.org/mod_mbox/jena-users/201210.mbox/%3C508B0C
>>54.3080...@apache.org%3E
>> >
>> > --
>> > diogo patrão
>> >
>>
>>
>>
>> --
>> I like: Like Like - The likeliest place on the web<
>> http://like-like.xenei.com>
>> Identity: https://www.identify.nu/user.php?cla...@xenei.com
>> LinkedIn: http://www.linkedin.com/in/claudewarren
>>
