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Posted to users@jena.apache.org by Martin Weitzel <me...@mweitzel.com> on 2011/11/08 21:03:14 UTC
Passing a parameter to a Jena ARQ custom Property Function
Hi there,
I am using Jena within a Spring MVC web application as interface for a rdf
knowledge base. The main application for this knowledge base is to be
queried with SPARQL for the best fitting (logistic) service provider for a
certain conext.
I extended the ARQ with a property function, which task is to calculate a
"fitness" value for each service provider. The problem is, that the
calculation is depending on information that is only available within the
requesting query method (i.e. a given transportation path, that is needed
to calculate the distance from a service provider (stored in the knowledge
base) to the path (a request-thing)).
So, I am looking for a best practice to pass:
a) The object (reference) itself or
b) A Key for a ConcurrentMap
to the property function calculating the fitness. I tried to extend the
SPARQL query by binding a string literal to a new variable, so that it
would be available in the binding or the context, but without success. My
current solution is not threadsafe: The FitnessCalculator is registered via
a factory as shown here (http://jena.sourceforge.net/ARQ/extension.html).
The factory is a spring service and injects the query service reference to
the property function. The query method then saves the transport path
object in a public variable, that is accessable by the Property Function.
Obviously, this will have side effects in a multi-threaded environment.
I would appreciate any best practice tips!
-- Martin
Re: Passing a parameter to a Jena ARQ custom Property Function
Posted by Andy Seaborne <an...@apache.org>.
On 09/11/11 07:49, Martin Weitzel wrote:
> Ah okay, case solved. An healthy look into API and this works just fine:
>
> final QueryExecution queryExecution =
>>> QueryExecutionFactory.create(QueryFactory.create(queryString),
>>
>> requestModel);
>>
>>
>>> queryExecution.getContext().set(Symbol.create("TransportSection") ,
>>> transportSection);
>>
>>
> My "transportSection" is then available within the QueryContext of the
> property function execution.
>
> -- Martin
:-)
That's the best way. An initial binding for a varibale, e.,g. ?myParam
and passing ?myParam to your property function (list of args to be able
to get more than one arg in) shoudl also work but (1) old versions had a
bug on rewriting the constant into the query for property functions and
(2) that's what the context is for anyway.
Andy
>
>
> 2011/11/8 Martin Weitzel<me...@mweitzel.com>
>
>> Hi there,
>>
>> I am using Jena within a Spring MVC web application as interface for a rdf
>> knowledge base. The main application for this knowledge base is to be
>> queried with SPARQL for the best fitting (logistic) service provider for a
>> certain conext.
>>
>> I extended the ARQ with a property function, which task is to calculate a
>> "fitness" value for each service provider. The problem is, that the
>> calculation is depending on information that is only available within the
>> requesting query method (i.e. a given transportation path, that is
>> needed to calculate the distance from a service provider (stored in the
>> knowledge base) to the path (a request-thing)).
>>
>> So, I am looking for a best practice to pass:
>>
>> a) The object (reference) itself or
>> b) A Key for a ConcurrentMap
>>
>> to the property function calculating the fitness. I tried to extend the
>> SPARQL query by binding a string literal to a new variable, so that it
>> would be available in the binding or the context, but without success. My
>> current solution is not threadsafe: The FitnessCalculator is registered via
>> a factory as shown here (http://jena.sourceforge.net/ARQ/extension.html).
>> The factory is a spring service and injects the query service reference to
>> the property function. The query method then saves the transport path
>> object in a public variable, that is accessable by the Property Function.
>> Obviously, this will have side effects in a multi-threaded environment.
>>
>> I would appreciate any best practice tips!
>>
>> -- Martin
>>
>
Re: Passing a parameter to a Jena ARQ custom Property Function
Posted by Martin Weitzel <me...@mweitzel.com>.
Ah okay, case solved. An healthy look into API and this works just fine:
final QueryExecution queryExecution =
>> QueryExecutionFactory.create(QueryFactory.create(queryString),
>
> requestModel);
>
>
>> queryExecution.getContext().set(Symbol.create("TransportSection") ,
>> transportSection);
>
>
My "transportSection" is then available within the QueryContext of the
property function execution.
-- Martin
2011/11/8 Martin Weitzel <me...@mweitzel.com>
> Hi there,
>
> I am using Jena within a Spring MVC web application as interface for a rdf
> knowledge base. The main application for this knowledge base is to be
> queried with SPARQL for the best fitting (logistic) service provider for a
> certain conext.
>
> I extended the ARQ with a property function, which task is to calculate a
> "fitness" value for each service provider. The problem is, that the
> calculation is depending on information that is only available within the
> requesting query method (i.e. a given transportation path, that is
> needed to calculate the distance from a service provider (stored in the
> knowledge base) to the path (a request-thing)).
>
> So, I am looking for a best practice to pass:
>
> a) The object (reference) itself or
> b) A Key for a ConcurrentMap
>
> to the property function calculating the fitness. I tried to extend the
> SPARQL query by binding a string literal to a new variable, so that it
> would be available in the binding or the context, but without success. My
> current solution is not threadsafe: The FitnessCalculator is registered via
> a factory as shown here (http://jena.sourceforge.net/ARQ/extension.html).
> The factory is a spring service and injects the query service reference to
> the property function. The query method then saves the transport path
> object in a public variable, that is accessable by the Property Function.
> Obviously, this will have side effects in a multi-threaded environment.
>
> I would appreciate any best practice tips!
>
> -- Martin
>