[Activerdf] query results metadata

[Eric Hanson]

Eyal Oren wrote:
> On 10/03/06/10/06 21:31 -0700, Eric Hanson wrote:
>> Hi all,
>> I'm using the Redland Adapter in the ActiveRDF 0.2.  Is it possible to
>> get query results metadata like the number of rows returned, the column
>> names, etc?  I'm guessing this is something you're addressing in the
>> next version but if there's a way to do it now that'd be cool.
> Hi,
> 
> Currently indeed there is not such information, as we return simple
> arrays or single values.  I could add this easily in the new
> development, but what would be the use exactly?
> 
> First, the number of results you can get from results.size (it's an
> array), and the number of query bindings you should know since you asked
> the query yourselve? Or am I missing something here?
> Can you explain me the usage scenario?

Get size from the array -- that makes sense.

The other thing is the "column" names that a SPARQL query returns.  I
want the user to be able to enter in an arbitrary query in form, and
then display the results as a table, with the column names labeled at
the top.  So if I do:

SELECT ?s ?p ?o WHERE {?s ?p ?o}

It should generate a three-column table with

<tr>
	<th>s</th>
	<th>p</th>
	<th>o</th>
</tr>

at the top.

Another use-case is generating SPARQL query results in JSON format.  The
SPARQL JSON serialization [1] requires a "head" section that looks like:

{
  "head": { "vars": [ "book" , "title" ]
  } ,
  ...
}

Make sense?  It might mean moving away from pure array results to a
QueryResults object or something, I don't know if you're down with that...

Thanks,
Eric

[1] http://www.w3.org/2001/sw/DataAccess/json-sparql/