Can I pass a SPARQL query and return only the regex pattern

[Saud Al-Jaloud <sz...@ecs.soton.ac.uk>]

Hi,

Is there a way with Jena api to pass a SPARQL query that can return the regex pattern?

For example:
A query like: "PREFIX  dc:  <http://purl.org/dc/elements/1.1/>
SELECT  ?title
WHERE   { ?x dc:title ?title
          FILTER regex(?title, "^SPARQL") 
        }"
Should return "^SPARQL". if there are more than one regex, it should return all regex patterns.

I'm already using my version of regex search to extract the pattern, though it still misses some patterns. I'd think using Jena is more certain in returning the exact pattern.
The finest I could get to is to return the query pattern using Query.getQueryPattern(); not any further.

Thanks,
Saud.

Re: Can I pass a SPARQL query and return only the regex pattern

[Andy Seaborne <an...@apache.org>]

On 07/09/13 00:30, Saud Al-Jaloud wrote:
> Hi,
>
> Is there a way with Jena api to pass a SPARQL query that can return the regex pattern?
>
> For example:
> A query like: "PREFIX  dc:  <http://purl.org/dc/elements/1.1/>
> SELECT  ?title
> WHERE   { ?x dc:title ?title
>            FILTER regex(?title, "^SPARQL")
>          }"
> Should return "^SPARQL". if there are more than one regex, it should return all regex patterns.
>
> I'm already using my version of regex search to extract the pattern, though it still misses some patterns. I'd think using Jena is more certain in returning the exact pattern.
> The finest I could get to is to return the query pattern using Query.getQueryPattern(); not any further.
>
> Thanks,
> Saud.
>

Query.getQueryPattern() returns an Element.  You can walk that using a 
ElementVisitor.

As you're working with the internals of the system, you'll probably want 
to look at the source code.  If you look at the classhierarchy (in 
Eclipse for example) of ElementVisitor, you'll see some examples.

You may find work with the algebra easier.
http://jena.apache.org/documentation/query/algebra.html

and the OpVisitor, of which there are lots of examples in the code.

	Andy