incubator-clerezza-dev mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From Andy Seaborne <a...@apache.org>
Subject Re: Query over multiple named graphs
Date Tue, 08 Jan 2013 17:29:57 GMT
On 08/01/13 15:05, Minto van der Sluis wrote:
> Hi Reto,
>
> Thanks for your answer.
>
> It's not that I want to merge multiple named graphs together to perform
> a query. I already achieved that as a workaround by adding new triples
> to both a named graph and a default graph. Like this I can query the
> default graph.
>
> What I actually try to achieve is find all named graphs the meet certain
> requirements. For instance the following simple query to return then
> names of all named graph.
>
> |SELECT DISTINCT ?g
> WHERE {
>    GRAPH ?g {
>      ?s ?p ?o
>    }
> }|
>

a better query is:

SELECT ?g { GRAPH ?g {} }

	Andy


>
> This query contains no FROM clause. So I guess the supplied graph
> (second argument) is still used.
>
> The workaround I currently use is satisfactory for the time being, but
> does not meet the requirements I have for the near future. So I have to
> come up with something one way or another.
>
> Regards,
>
> Minto
>
> Op 8-1-2013 14:16, Reto Bachmann-Gmür schreef:
>> Hi Minto,
>>
>> The defaultGraph passed as second argument is ignered if a FROM clause is
>> present in your query, otherwise this is used as default Graph and other
>> graphs can be access using "FROM NAMED".
>>
>> If you want to rund your query about afainst the union of several graphs
>> you should use UnionMGraph as Tommaso pointed out. If this is your usecase
>> we should keep this in mind for the fast-lane to be implemented.
>>
>> Cheers,
>> Reto
>>
>> On Tue, Jan 8, 2013 at 8:53 AM, Tommaso Teofili
>> <tommaso.teofili@gmail.com>wrote:
>>
>>> Hi Minto,
>>>
>>> I think that you should use a union graph (UnionMGraph) over your
>>> underlying named graphs and that should work as expected.
>>>
>>> I hope this helps,
>>> Tommaso
>>>
>>>
>>> 2013/1/6 Minto van der Sluis <minto@xup.nl>
>>>
>>>> Hi folks,
>>>>
>>>> Currently I am using clerezza with a Jena TDB storage backend to store
>>>> multiple named graphs.
>>>>
>>>> Now I wonder how to perform a query over these named graphs. I can use
>>>> the following command:
>>>>
>>>>      TcManager.executeSparqlQuery( query, ? )
>>>>
>>>> But what should be used as the triple collection? If the default graph,
>>>> how do I specify that?
>>>>
>>>> Regards,
>>>>
>>>> Minto van der Sluis
>>>> Software innovator / renovator
>>>> Xup BV
>>>>
>
>


Mime
View raw message