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Posted to dev@stanbol.apache.org by Andrea Giovanni Nuzzolese <nu...@cs.unibo.it> on 2011/06/08 19:20:06 UTC
SPARQL serialization of FieldQuery
Hi,
I am trying to use the query service provided by the EntityHub.
The JSON field query I wrote is the following
{
"selected": ["http:\/\/www.w3.org\/2000\/01\/rdf-schema#label",
"http:\/\/www.w3.org\/1999\/02\/22-rdf-syntax-ns#type"],
"offset": "0",
"limit": "3",
"constraints": [
{
"type": "reference",
"field": "http:\/\/www.w3.org\/2002\/07\/owl#sameAs",
"value": "http:\/\/www4.wiwiss.fu-berlin.de\/factbook\/resource\/United_States",
}]
}
and aims to find all the owl:sameAs entities of the entity <http://www4.wiwiss.fu-berlin.de/factbook/resource/United_States> in DBpedia.
But instead of the graph with the expected results I always receive the error
javax.ws.rs.WebApplicationException: org.apache.stanbol.entityhub.servicesapi.site.ReferencedSiteException: Unable execute Query on remote site http://dbpedia.org/sparql
The sparql construct serialized by the EntityHub is the following
CONSTRUCT {
?id <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> ?v_1 .
?id <http://www.w3.org/2000/01/rdf-schema#label> ?v_2 .
<http://www.iks-project.eu/ontology/rick/query/QueryResultSet> <http://www.iks-project.eu/ontology/rick/query/queryResult> ?id .
}
WHERE {
{ {?id <http://www.w3.org/2002/07/owl#sameAs> <http://www4.wiwiss.fu-berlin.de/factbook/resource/United_States> }}
{ OPTIONAL { ?id <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> ?v_1 . } }
{ OPTIONAL { ?id <http://www.w3.org/2000/01/rdf-schema#label> ?v_2 . } }
}
ORDER BY DESC ( <LONG::IRI_RANK> (?id) ) LIMIT 3
If you try to run this construct directly on the SPARQL endpoint of dbpedia the response is always "Virtuoso 42000 Error The estimated execution time 0 (sec) exceeds the limit of 1500 (sec)."
It seems that the problem is in the graph patterns containing optional as they are bound to the whole default graph ( {OPTIONAL{triple pattern} } is equivalent to { {} OPTIONAL {triple pattern} }.
In fact the query works properly both if you substitute the three graph patterns into one graph pattern as follows
...
WHERE {
?id <http://www.w3.org/2002/07/owl#sameAs> <http://www4.wiwiss.fu-berlin.de/factbook/resource/United_States> .
OPTIONAL { ?id <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> ?v_1 . }
OPTIONAL { ?id <http://www.w3.org/2000/01/rdf-schema#label> ?v_2 . }
}
...
and if you bind the optional to the global solution of the WHERE clause, i.e.
...
WHERE {
{{?id <http://www.w3.org/2002/07/owl#sameAs> <http://www4.wiwiss.fu-berlin.de/factbook/resource/United_States> . }}
OPTIONAL { ?id <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> ?v_1 . } .
OPTIONAL { ?id <http://www.w3.org/2000/01/rdf-schema#label> ?v_2 . }
}
...
Regards.
--
Andrea Giovanni Nuzzolese
Semantic Technology Laboratory (STLab)
Institute for Cognitive Science and Technology (ISTC)
National Research Council (CNR)
Via Nomentana 56, Roma - Itay
Re: SPARQL serialization of FieldQuery
Posted by Andrea Giovanni Nuzzolese <nu...@cs.unibo.it>.
Hi,
I am fear that right now subqueries are the only walk around to this sort of problem with a single query.
A possible solution in SPARQL1.0 is to split the query into two different queries:
(i) select the right number of entities according to the limit
(ii) construct the graph with the required information related to the selected entities
Just to detail the problem, since 2009 there is already a proposal of a new feature for an object-oriented like limit [1].
I do not know any concrete implementation of that sort of limit.
Regards.
--
Andrea
[1] http://www.w3.org/2009/sparql/wiki/Feature:LimitPerResource
On Jun 13, 2011, at 10:54 PM, Rupert Westenthaler wrote:
> Hi
>
> Is there also a possibility to do a similar thing by using SPARQL 1.0?
> It is already a pain to adapt SPARQL 1.0 queries to implementation
> specific features. I guess that is even worse with SPARQL 1.1.
>
> regards
> Rupert
>
>
> On Mon, Jun 13, 2011 at 7:45 PM, Andrea Giovanni Nuzzolese
> <nu...@cs.unibo.it> wrote:
>> Hi Rupert, all
>>
>> I want to add only one consideration that I missed in the previous email.
>> Subqueries are completely in SPARQL1.1, but both Jena [1] (with syntaxARQ) and Virtuoso support it as you can easily see querying DBpedia.
>>
>> Best.
>>
>> --
>> Andrea Giovanni Nuzzolese
>> Semantic Technology Laboratory (STLab)
>> Institute for Cognitive Science and Technology (ISTC)
>> National Research Council (CNR)
>> Via Nomentana 56, Roma - Itay
>>
>>
>> [1] http://jena.sourceforge.net/ARQ/sub-select.html
>>
>>
>> On Jun 13, 2011, at 7:30 PM, Andrea Giovanni Nuzzolese wrote:
>>
>>> Hi Rupert, all
>>>
>>> my impression is that the limit in the construct should work only at the level of the constraints that the user have provided in the FieldQuery.
>>> To be to be as clearly as possible I take again my previous query example in which I want to find at most 3 same as entities of <http://www4.wiwiss.fu-berlin.de/factbook/resource/United_States>
>>>
>>> {
>>> "selected": ["http:\/\/www.w3.org\/2000\/01\/rdf-schema#label", "http:\/\/www.w3.org\/1999\/02\/22-rdf-syntax-ns#type"],
>>> "offset": "0",
>>> "limit": "3",
>>> "constraints": [ {"type": "reference", "field": "http:\/\/www.w3.org\/2002\/07\/owl#sameAs", "value": "http:\/\/www4.wiwiss.fu-berlin.de\/factbook\/resource\/United_States"}]
>>> }
>>>
>>> To select at most the right number of entities the query should be converted into a construct like the following
>>>
>>> CONSTRUCT {
>>> ?id <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> ?v_1 .
>>> ?id <http://www.w3.org/2000/01/rdf-schema#label> ?v_2 .
>>> <http://www.iks-project.eu/ontology/rick/query/QueryResultSet>
>>> <http://www.iks-project.eu/ontology/rick/query/queryResult> ?id .
>>> }
>>> WHERE {
>>> {
>>> SELECT ?id
>>> WHERE { ?id <http://www.w3.org/2002/07/owl#sameAs><http://www4.wiwiss.fu-berlin.de/factbook/resource/United_States> }
>>> LIMIT 3
>>> }
>>> OPTIONAL { ?id <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> ?v_1 . } .
>>> OPTIONAL { ?id <http://www.w3.org/2000/01/rdf-schema#label> ?v_2 . }
>>> }
>>> ORDER BY DESC ( <LONG::IRI_RANK> (?id) )
>>>
>>> In this way the limit works on the number of entities to fetch and not the number of solutions.
>>>
>>> Best.
>>>
>>> --
>>> Andrea Giovanni Nuzzolese
>>> Semantic Technology Laboratory (STLab)
>>> Institute for Cognitive Science and Technology (ISTC)
>>> National Research Council (CNR)
>>> Via Nomentana 56, Roma - Itay
>>>
>>> On Jun 13, 2011, at 6:47 PM, Rupert Westenthaler wrote:
>>>
>>>> Hi Andrea, all
>>>>
>>>> While working on this I discovered something else:
>>>>
>>>> The "LIMIT" of SPARQL is based on solutions. For the Entityhub its
>>>> semantic is that is defines the number of entities to select.
>>>>
>>>> When selecting multiple variables there is the possibility (actually
>>>> it is very likely) that there are multiple solutions/entity. Therefore
>>>> it can no longer be predicted how many entities are selected by a
>>>> SPARQL query. This also affects CONSTRUCT queries as it will restrict
>>>> the numbers of triples added to the resulting graph.
>>>>
>>>> Is if there is any possibility to work around this problem?
>>>>
>>>> best
>>>> Rupert Westenthaler
>>>>
>>>> On Thu, Jun 9, 2011 at 3:57 PM, Andrea Giovanni Nuzzolese
>>>> <nu...@cs.unibo.it> wrote:
>>>>> The issue is STANBOL-222.
>>>>>
>>>>> Best.
>>>>> Andrea
>>>>>
>>>>> On Jun 9, 2011, at 9:54 AM, Rupert Westenthaler wrote:
>>>>>
>>>>>> Hi
>>>>>>
>>>>>> Thx a lot. I was aware of the fact that optional constraints do cause
>>>>>> this problem, but I have not known that rewriting the query like this
>>>>>> can solve this problem.
>>>>>> I will try to change the generation of SPARQL queries tomorrow on the
>>>>>> way back from Berlin to Salzburg.
>>>>>>
>>>>>> would be nice if you could create a JIRA issue for that
>>>>>>
>>>>>> best
>>>>>> Rupert
>>>>>>
>>>>>> On Wed, Jun 8, 2011 at 7:20 PM, Andrea Giovanni Nuzzolese
>>>>>> <nu...@cs.unibo.it> wrote:
>>>>>>> Hi,
>>>>>>> I am trying to use the query service provided by the EntityHub.
>>>>>>> The JSON field query I wrote is the following
>>>>>>> {
>>>>>>> "selected": ["http:\/\/www.w3.org\/2000\/01\/rdf-schema#label",
>>>>>>> "http:\/\/www.w3.org\/1999\/02\/22-rdf-syntax-ns#type"],
>>>>>>> "offset": "0",
>>>>>>> "limit": "3",
>>>>>>> "constraints": [
>>>>>>> {
>>>>>>> "type": "reference",
>>>>>>> "field": "http:\/\/www.w3.org\/2002\/07\/owl#sameAs",
>>>>>>> "value":
>>>>>>> "http:\/\/www4.wiwiss.fu-berlin.de\/factbook\/resource\/United_States",
>>>>>>> }]
>>>>>>> }
>>>>>>> and aims to find all the owl:sameAs entities of the entity
>>>>>>> <http://www4.wiwiss.fu-berlin.de/factbook/resource/United_States> in
>>>>>>> DBpedia.
>>>>>>> But instead of the graph with the expected results I always receive the
>>>>>>> error
>>>>>>> javax.ws.rs.WebApplicationException:
>>>>>>> org.apache.stanbol.entityhub.servicesapi.site.ReferencedSiteException:
>>>>>>> Unable execute Query on remote site http://dbpedia.org/sparql
>>>>>>> The sparql construct serialized by the EntityHub is the following
>>>>>>> CONSTRUCT {
>>>>>>> ?id <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> ?v_1 .
>>>>>>> ?id <http://www.w3.org/2000/01/rdf-schema#label> ?v_2 .
>>>>>>> <http://www.iks-project.eu/ontology/rick/query/QueryResultSet>
>>>>>>> <http://www.iks-project.eu/ontology/rick/query/queryResult> ?id .
>>>>>>> }
>>>>>>> WHERE {
>>>>>>> { {?id <http://www.w3.org/2002/07/owl#sameAs>
>>>>>>> <http://www4.wiwiss.fu-berlin.de/factbook/resource/United_States> }}
>>>>>>> { OPTIONAL { ?id <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> ?v_1 . }
>>>>>>> }
>>>>>>> { OPTIONAL { ?id <http://www.w3.org/2000/01/rdf-schema#label> ?v_2 . } }
>>>>>>> }
>>>>>>> ORDER BY DESC ( <LONG::IRI_RANK> (?id) ) LIMIT 3
>>>>>>> If you try to run this construct directly on the SPARQL endpoint of dbpedia
>>>>>>> the response is always "Virtuoso 42000 Error The estimated execution time 0
>>>>>>> (sec) exceeds the limit of 1500 (sec)."
>>>>>>> It seems that the problem is in the graph patterns containing optional as
>>>>>>> they are bound to the whole default graph ( {OPTIONAL{triple pattern} } is
>>>>>>> equivalent to { {} OPTIONAL {triple pattern} }.
>>>>>>> In fact the query works properly both if you substitute the three graph
>>>>>>> patterns into one graph pattern as follows
>>>>>>> ...
>>>>>>> WHERE {
>>>>>>> ?id <http://www.w3.org/2002/07/owl#sameAs>
>>>>>>> <http://www4.wiwiss.fu-berlin.de/factbook/resource/United_States> .
>>>>>>> OPTIONAL { ?id <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> ?v_1 . }
>>>>>>> OPTIONAL { ?id <http://www.w3.org/2000/01/rdf-schema#label> ?v_2 . }
>>>>>>> }
>>>>>>> ...
>>>>>>>
>>>>>>> and if you bind the optional to the global solution of the WHERE clause,
>>>>>>> i.e.
>>>>>>> ...
>>>>>>> WHERE {
>>>>>>> {{?id <http://www.w3.org/2002/07/owl#sameAs>
>>>>>>> <http://www4.wiwiss.fu-berlin.de/factbook/resource/United_States> . }}
>>>>>>> OPTIONAL { ?id <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> ?v_1 . } .
>>>>>>> OPTIONAL { ?id <http://www.w3.org/2000/01/rdf-schema#label> ?v_2 . }
>>>>>>> }
>>>>>>> ...
>>>>>>>
>>>>>>>
>>>>>>> Regards.
>>>>>>> --
>>>>>>> Andrea Giovanni Nuzzolese
>>>>>>> Semantic Technology Laboratory (STLab)
>>>>>>> Institute for Cognitive Science and Technology (ISTC)
>>>>>>> National Research Council (CNR)
>>>>>>> Via Nomentana 56, Roma - Itay
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>> --
>>>>>> | Rupert Westenthaler rupert.westenthaler@gmail.com
>>>>>> | Bodenlehenstraße 11 ++43-699-11108907
>>>>>> | A-5500 Bischofshofen
>>>>>
>>>>> --
>>>>> Andrea Giovanni Nuzzolese
>>>>> Semantic Technology Laboratory (STLab)
>>>>> Institute for Cognitive Science and Technology (ISTC)
>>>>> National Research Council (CNR)
>>>>> Via Nomentana 56, Roma - Itay
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>
>>>>
>>>>
>>>> --
>>>> | Rupert Westenthaler rupert.westenthaler@gmail.com
>>>> | Bodenlehenstraße 11 ++43-699-11108907
>>>> | A-5500 Bischofshofen
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>
>>
>>
>>
>>
>>
>>
>>
>
>
>
> --
> | Rupert Westenthaler rupert.westenthaler@gmail.com
> | Bodenlehenstraße 11 ++43-699-11108907
> | A-5500 Bischofshofen
Re: SPARQL serialization of FieldQuery
Posted by Rupert Westenthaler <ru...@gmail.com>.
Hi
Is there also a possibility to do a similar thing by using SPARQL 1.0?
It is already a pain to adapt SPARQL 1.0 queries to implementation
specific features. I guess that is even worse with SPARQL 1.1.
regards
Rupert
On Mon, Jun 13, 2011 at 7:45 PM, Andrea Giovanni Nuzzolese
<nu...@cs.unibo.it> wrote:
> Hi Rupert, all
>
> I want to add only one consideration that I missed in the previous email.
> Subqueries are completely in SPARQL1.1, but both Jena [1] (with syntaxARQ) and Virtuoso support it as you can easily see querying DBpedia.
>
> Best.
>
> --
> Andrea Giovanni Nuzzolese
> Semantic Technology Laboratory (STLab)
> Institute for Cognitive Science and Technology (ISTC)
> National Research Council (CNR)
> Via Nomentana 56, Roma - Itay
>
>
> [1] http://jena.sourceforge.net/ARQ/sub-select.html
>
>
> On Jun 13, 2011, at 7:30 PM, Andrea Giovanni Nuzzolese wrote:
>
>> Hi Rupert, all
>>
>> my impression is that the limit in the construct should work only at the level of the constraints that the user have provided in the FieldQuery.
>> To be to be as clearly as possible I take again my previous query example in which I want to find at most 3 same as entities of <http://www4.wiwiss.fu-berlin.de/factbook/resource/United_States>
>>
>> {
>> "selected": ["http:\/\/www.w3.org\/2000\/01\/rdf-schema#label", "http:\/\/www.w3.org\/1999\/02\/22-rdf-syntax-ns#type"],
>> "offset": "0",
>> "limit": "3",
>> "constraints": [ {"type": "reference", "field": "http:\/\/www.w3.org\/2002\/07\/owl#sameAs", "value": "http:\/\/www4.wiwiss.fu-berlin.de\/factbook\/resource\/United_States"}]
>> }
>>
>> To select at most the right number of entities the query should be converted into a construct like the following
>>
>> CONSTRUCT {
>> ?id <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> ?v_1 .
>> ?id <http://www.w3.org/2000/01/rdf-schema#label> ?v_2 .
>> <http://www.iks-project.eu/ontology/rick/query/QueryResultSet>
>> <http://www.iks-project.eu/ontology/rick/query/queryResult> ?id .
>> }
>> WHERE {
>> {
>> SELECT ?id
>> WHERE { ?id <http://www.w3.org/2002/07/owl#sameAs><http://www4.wiwiss.fu-berlin.de/factbook/resource/United_States> }
>> LIMIT 3
>> }
>> OPTIONAL { ?id <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> ?v_1 . } .
>> OPTIONAL { ?id <http://www.w3.org/2000/01/rdf-schema#label> ?v_2 . }
>> }
>> ORDER BY DESC ( <LONG::IRI_RANK> (?id) )
>>
>> In this way the limit works on the number of entities to fetch and not the number of solutions.
>>
>> Best.
>>
>> --
>> Andrea Giovanni Nuzzolese
>> Semantic Technology Laboratory (STLab)
>> Institute for Cognitive Science and Technology (ISTC)
>> National Research Council (CNR)
>> Via Nomentana 56, Roma - Itay
>>
>> On Jun 13, 2011, at 6:47 PM, Rupert Westenthaler wrote:
>>
>>> Hi Andrea, all
>>>
>>> While working on this I discovered something else:
>>>
>>> The "LIMIT" of SPARQL is based on solutions. For the Entityhub its
>>> semantic is that is defines the number of entities to select.
>>>
>>> When selecting multiple variables there is the possibility (actually
>>> it is very likely) that there are multiple solutions/entity. Therefore
>>> it can no longer be predicted how many entities are selected by a
>>> SPARQL query. This also affects CONSTRUCT queries as it will restrict
>>> the numbers of triples added to the resulting graph.
>>>
>>> Is if there is any possibility to work around this problem?
>>>
>>> best
>>> Rupert Westenthaler
>>>
>>> On Thu, Jun 9, 2011 at 3:57 PM, Andrea Giovanni Nuzzolese
>>> <nu...@cs.unibo.it> wrote:
>>>> The issue is STANBOL-222.
>>>>
>>>> Best.
>>>> Andrea
>>>>
>>>> On Jun 9, 2011, at 9:54 AM, Rupert Westenthaler wrote:
>>>>
>>>>> Hi
>>>>>
>>>>> Thx a lot. I was aware of the fact that optional constraints do cause
>>>>> this problem, but I have not known that rewriting the query like this
>>>>> can solve this problem.
>>>>> I will try to change the generation of SPARQL queries tomorrow on the
>>>>> way back from Berlin to Salzburg.
>>>>>
>>>>> would be nice if you could create a JIRA issue for that
>>>>>
>>>>> best
>>>>> Rupert
>>>>>
>>>>> On Wed, Jun 8, 2011 at 7:20 PM, Andrea Giovanni Nuzzolese
>>>>> <nu...@cs.unibo.it> wrote:
>>>>>> Hi,
>>>>>> I am trying to use the query service provided by the EntityHub.
>>>>>> The JSON field query I wrote is the following
>>>>>> {
>>>>>> "selected": ["http:\/\/www.w3.org\/2000\/01\/rdf-schema#label",
>>>>>> "http:\/\/www.w3.org\/1999\/02\/22-rdf-syntax-ns#type"],
>>>>>> "offset": "0",
>>>>>> "limit": "3",
>>>>>> "constraints": [
>>>>>> {
>>>>>> "type": "reference",
>>>>>> "field": "http:\/\/www.w3.org\/2002\/07\/owl#sameAs",
>>>>>> "value":
>>>>>> "http:\/\/www4.wiwiss.fu-berlin.de\/factbook\/resource\/United_States",
>>>>>> }]
>>>>>> }
>>>>>> and aims to find all the owl:sameAs entities of the entity
>>>>>> <http://www4.wiwiss.fu-berlin.de/factbook/resource/United_States> in
>>>>>> DBpedia.
>>>>>> But instead of the graph with the expected results I always receive the
>>>>>> error
>>>>>> javax.ws.rs.WebApplicationException:
>>>>>> org.apache.stanbol.entityhub.servicesapi.site.ReferencedSiteException:
>>>>>> Unable execute Query on remote site http://dbpedia.org/sparql
>>>>>> The sparql construct serialized by the EntityHub is the following
>>>>>> CONSTRUCT {
>>>>>> ?id <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> ?v_1 .
>>>>>> ?id <http://www.w3.org/2000/01/rdf-schema#label> ?v_2 .
>>>>>> <http://www.iks-project.eu/ontology/rick/query/QueryResultSet>
>>>>>> <http://www.iks-project.eu/ontology/rick/query/queryResult> ?id .
>>>>>> }
>>>>>> WHERE {
>>>>>> { {?id <http://www.w3.org/2002/07/owl#sameAs>
>>>>>> <http://www4.wiwiss.fu-berlin.de/factbook/resource/United_States> }}
>>>>>> { OPTIONAL { ?id <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> ?v_1 . }
>>>>>> }
>>>>>> { OPTIONAL { ?id <http://www.w3.org/2000/01/rdf-schema#label> ?v_2 . } }
>>>>>> }
>>>>>> ORDER BY DESC ( <LONG::IRI_RANK> (?id) ) LIMIT 3
>>>>>> If you try to run this construct directly on the SPARQL endpoint of dbpedia
>>>>>> the response is always "Virtuoso 42000 Error The estimated execution time 0
>>>>>> (sec) exceeds the limit of 1500 (sec)."
>>>>>> It seems that the problem is in the graph patterns containing optional as
>>>>>> they are bound to the whole default graph ( {OPTIONAL{triple pattern} } is
>>>>>> equivalent to { {} OPTIONAL {triple pattern} }.
>>>>>> In fact the query works properly both if you substitute the three graph
>>>>>> patterns into one graph pattern as follows
>>>>>> ...
>>>>>> WHERE {
>>>>>> ?id <http://www.w3.org/2002/07/owl#sameAs>
>>>>>> <http://www4.wiwiss.fu-berlin.de/factbook/resource/United_States> .
>>>>>> OPTIONAL { ?id <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> ?v_1 . }
>>>>>> OPTIONAL { ?id <http://www.w3.org/2000/01/rdf-schema#label> ?v_2 . }
>>>>>> }
>>>>>> ...
>>>>>>
>>>>>> and if you bind the optional to the global solution of the WHERE clause,
>>>>>> i.e.
>>>>>> ...
>>>>>> WHERE {
>>>>>> {{?id <http://www.w3.org/2002/07/owl#sameAs>
>>>>>> <http://www4.wiwiss.fu-berlin.de/factbook/resource/United_States> . }}
>>>>>> OPTIONAL { ?id <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> ?v_1 . } .
>>>>>> OPTIONAL { ?id <http://www.w3.org/2000/01/rdf-schema#label> ?v_2 . }
>>>>>> }
>>>>>> ...
>>>>>>
>>>>>>
>>>>>> Regards.
>>>>>> --
>>>>>> Andrea Giovanni Nuzzolese
>>>>>> Semantic Technology Laboratory (STLab)
>>>>>> Institute for Cognitive Science and Technology (ISTC)
>>>>>> National Research Council (CNR)
>>>>>> Via Nomentana 56, Roma - Itay
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>
>>>>>
>>>>>
>>>>> --
>>>>> | Rupert Westenthaler rupert.westenthaler@gmail.com
>>>>> | Bodenlehenstraße 11 ++43-699-11108907
>>>>> | A-5500 Bischofshofen
>>>>
>>>> --
>>>> Andrea Giovanni Nuzzolese
>>>> Semantic Technology Laboratory (STLab)
>>>> Institute for Cognitive Science and Technology (ISTC)
>>>> National Research Council (CNR)
>>>> Via Nomentana 56, Roma - Itay
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>
>>>
>>>
>>> --
>>> | Rupert Westenthaler rupert.westenthaler@gmail.com
>>> | Bodenlehenstraße 11 ++43-699-11108907
>>> | A-5500 Bischofshofen
>>
>>
>>
>>
>>
>>
>>
>>
>
>
>
>
>
>
>
>
--
| Rupert Westenthaler rupert.westenthaler@gmail.com
| Bodenlehenstraße 11 ++43-699-11108907
| A-5500 Bischofshofen
Re: SPARQL serialization of FieldQuery
Posted by Andrea Giovanni Nuzzolese <nu...@cs.unibo.it>.
Hi Rupert, all
I want to add only one consideration that I missed in the previous email.
Subqueries are completely in SPARQL1.1, but both Jena [1] (with syntaxARQ) and Virtuoso support it as you can easily see querying DBpedia.
Best.
--
Andrea Giovanni Nuzzolese
Semantic Technology Laboratory (STLab)
Institute for Cognitive Science and Technology (ISTC)
National Research Council (CNR)
Via Nomentana 56, Roma - Itay
[1] http://jena.sourceforge.net/ARQ/sub-select.html
On Jun 13, 2011, at 7:30 PM, Andrea Giovanni Nuzzolese wrote:
> Hi Rupert, all
>
> my impression is that the limit in the construct should work only at the level of the constraints that the user have provided in the FieldQuery.
> To be to be as clearly as possible I take again my previous query example in which I want to find at most 3 same as entities of <http://www4.wiwiss.fu-berlin.de/factbook/resource/United_States>
>
> {
> "selected": ["http:\/\/www.w3.org\/2000\/01\/rdf-schema#label", "http:\/\/www.w3.org\/1999\/02\/22-rdf-syntax-ns#type"],
> "offset": "0",
> "limit": "3",
> "constraints": [ {"type": "reference", "field": "http:\/\/www.w3.org\/2002\/07\/owl#sameAs", "value": "http:\/\/www4.wiwiss.fu-berlin.de\/factbook\/resource\/United_States"}]
> }
>
> To select at most the right number of entities the query should be converted into a construct like the following
>
> CONSTRUCT {
> ?id <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> ?v_1 .
> ?id <http://www.w3.org/2000/01/rdf-schema#label> ?v_2 .
> <http://www.iks-project.eu/ontology/rick/query/QueryResultSet>
> <http://www.iks-project.eu/ontology/rick/query/queryResult> ?id .
> }
> WHERE {
> {
> SELECT ?id
> WHERE { ?id <http://www.w3.org/2002/07/owl#sameAs><http://www4.wiwiss.fu-berlin.de/factbook/resource/United_States> }
> LIMIT 3
> }
> OPTIONAL { ?id <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> ?v_1 . } .
> OPTIONAL { ?id <http://www.w3.org/2000/01/rdf-schema#label> ?v_2 . }
> }
> ORDER BY DESC ( <LONG::IRI_RANK> (?id) )
>
> In this way the limit works on the number of entities to fetch and not the number of solutions.
>
> Best.
>
> --
> Andrea Giovanni Nuzzolese
> Semantic Technology Laboratory (STLab)
> Institute for Cognitive Science and Technology (ISTC)
> National Research Council (CNR)
> Via Nomentana 56, Roma - Itay
>
> On Jun 13, 2011, at 6:47 PM, Rupert Westenthaler wrote:
>
>> Hi Andrea, all
>>
>> While working on this I discovered something else:
>>
>> The "LIMIT" of SPARQL is based on solutions. For the Entityhub its
>> semantic is that is defines the number of entities to select.
>>
>> When selecting multiple variables there is the possibility (actually
>> it is very likely) that there are multiple solutions/entity. Therefore
>> it can no longer be predicted how many entities are selected by a
>> SPARQL query. This also affects CONSTRUCT queries as it will restrict
>> the numbers of triples added to the resulting graph.
>>
>> Is if there is any possibility to work around this problem?
>>
>> best
>> Rupert Westenthaler
>>
>> On Thu, Jun 9, 2011 at 3:57 PM, Andrea Giovanni Nuzzolese
>> <nu...@cs.unibo.it> wrote:
>>> The issue is STANBOL-222.
>>>
>>> Best.
>>> Andrea
>>>
>>> On Jun 9, 2011, at 9:54 AM, Rupert Westenthaler wrote:
>>>
>>>> Hi
>>>>
>>>> Thx a lot. I was aware of the fact that optional constraints do cause
>>>> this problem, but I have not known that rewriting the query like this
>>>> can solve this problem.
>>>> I will try to change the generation of SPARQL queries tomorrow on the
>>>> way back from Berlin to Salzburg.
>>>>
>>>> would be nice if you could create a JIRA issue for that
>>>>
>>>> best
>>>> Rupert
>>>>
>>>> On Wed, Jun 8, 2011 at 7:20 PM, Andrea Giovanni Nuzzolese
>>>> <nu...@cs.unibo.it> wrote:
>>>>> Hi,
>>>>> I am trying to use the query service provided by the EntityHub.
>>>>> The JSON field query I wrote is the following
>>>>> {
>>>>> "selected": ["http:\/\/www.w3.org\/2000\/01\/rdf-schema#label",
>>>>> "http:\/\/www.w3.org\/1999\/02\/22-rdf-syntax-ns#type"],
>>>>> "offset": "0",
>>>>> "limit": "3",
>>>>> "constraints": [
>>>>> {
>>>>> "type": "reference",
>>>>> "field": "http:\/\/www.w3.org\/2002\/07\/owl#sameAs",
>>>>> "value":
>>>>> "http:\/\/www4.wiwiss.fu-berlin.de\/factbook\/resource\/United_States",
>>>>> }]
>>>>> }
>>>>> and aims to find all the owl:sameAs entities of the entity
>>>>> <http://www4.wiwiss.fu-berlin.de/factbook/resource/United_States> in
>>>>> DBpedia.
>>>>> But instead of the graph with the expected results I always receive the
>>>>> error
>>>>> javax.ws.rs.WebApplicationException:
>>>>> org.apache.stanbol.entityhub.servicesapi.site.ReferencedSiteException:
>>>>> Unable execute Query on remote site http://dbpedia.org/sparql
>>>>> The sparql construct serialized by the EntityHub is the following
>>>>> CONSTRUCT {
>>>>> ?id <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> ?v_1 .
>>>>> ?id <http://www.w3.org/2000/01/rdf-schema#label> ?v_2 .
>>>>> <http://www.iks-project.eu/ontology/rick/query/QueryResultSet>
>>>>> <http://www.iks-project.eu/ontology/rick/query/queryResult> ?id .
>>>>> }
>>>>> WHERE {
>>>>> { {?id <http://www.w3.org/2002/07/owl#sameAs>
>>>>> <http://www4.wiwiss.fu-berlin.de/factbook/resource/United_States> }}
>>>>> { OPTIONAL { ?id <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> ?v_1 . }
>>>>> }
>>>>> { OPTIONAL { ?id <http://www.w3.org/2000/01/rdf-schema#label> ?v_2 . } }
>>>>> }
>>>>> ORDER BY DESC ( <LONG::IRI_RANK> (?id) ) LIMIT 3
>>>>> If you try to run this construct directly on the SPARQL endpoint of dbpedia
>>>>> the response is always "Virtuoso 42000 Error The estimated execution time 0
>>>>> (sec) exceeds the limit of 1500 (sec)."
>>>>> It seems that the problem is in the graph patterns containing optional as
>>>>> they are bound to the whole default graph ( {OPTIONAL{triple pattern} } is
>>>>> equivalent to { {} OPTIONAL {triple pattern} }.
>>>>> In fact the query works properly both if you substitute the three graph
>>>>> patterns into one graph pattern as follows
>>>>> ...
>>>>> WHERE {
>>>>> ?id <http://www.w3.org/2002/07/owl#sameAs>
>>>>> <http://www4.wiwiss.fu-berlin.de/factbook/resource/United_States> .
>>>>> OPTIONAL { ?id <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> ?v_1 . }
>>>>> OPTIONAL { ?id <http://www.w3.org/2000/01/rdf-schema#label> ?v_2 . }
>>>>> }
>>>>> ...
>>>>>
>>>>> and if you bind the optional to the global solution of the WHERE clause,
>>>>> i.e.
>>>>> ...
>>>>> WHERE {
>>>>> {{?id <http://www.w3.org/2002/07/owl#sameAs>
>>>>> <http://www4.wiwiss.fu-berlin.de/factbook/resource/United_States> . }}
>>>>> OPTIONAL { ?id <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> ?v_1 . } .
>>>>> OPTIONAL { ?id <http://www.w3.org/2000/01/rdf-schema#label> ?v_2 . }
>>>>> }
>>>>> ...
>>>>>
>>>>>
>>>>> Regards.
>>>>> --
>>>>> Andrea Giovanni Nuzzolese
>>>>> Semantic Technology Laboratory (STLab)
>>>>> Institute for Cognitive Science and Technology (ISTC)
>>>>> National Research Council (CNR)
>>>>> Via Nomentana 56, Roma - Itay
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>
>>>>
>>>>
>>>> --
>>>> | Rupert Westenthaler rupert.westenthaler@gmail.com
>>>> | Bodenlehenstraße 11 ++43-699-11108907
>>>> | A-5500 Bischofshofen
>>>
>>> --
>>> Andrea Giovanni Nuzzolese
>>> Semantic Technology Laboratory (STLab)
>>> Institute for Cognitive Science and Technology (ISTC)
>>> National Research Council (CNR)
>>> Via Nomentana 56, Roma - Itay
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>
>>
>>
>> --
>> | Rupert Westenthaler rupert.westenthaler@gmail.com
>> | Bodenlehenstraße 11 ++43-699-11108907
>> | A-5500 Bischofshofen
>
>
>
>
>
>
>
>
Re: SPARQL serialization of FieldQuery
Posted by Andrea Giovanni Nuzzolese <nu...@cs.unibo.it>.
Hi Rupert, all
my impression is that the limit in the construct should work only at the level of the constraints that the user have provided in the FieldQuery.
To be to be as clearly as possible I take again my previous query example in which I want to find at most 3 same as entities of <http://www4.wiwiss.fu-berlin.de/factbook/resource/United_States>
{
"selected": ["http:\/\/www.w3.org\/2000\/01\/rdf-schema#label", "http:\/\/www.w3.org\/1999\/02\/22-rdf-syntax-ns#type"],
"offset": "0",
"limit": "3",
"constraints": [ {"type": "reference", "field": "http:\/\/www.w3.org\/2002\/07\/owl#sameAs", "value": "http:\/\/www4.wiwiss.fu-berlin.de\/factbook\/resource\/United_States"}]
}
To select at most the right number of entities the query should be converted into a construct like the following
CONSTRUCT {
?id <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> ?v_1 .
?id <http://www.w3.org/2000/01/rdf-schema#label> ?v_2 .
<http://www.iks-project.eu/ontology/rick/query/QueryResultSet>
<http://www.iks-project.eu/ontology/rick/query/queryResult> ?id .
}
WHERE {
{
SELECT ?id
WHERE { ?id <http://www.w3.org/2002/07/owl#sameAs><http://www4.wiwiss.fu-berlin.de/factbook/resource/United_States> }
LIMIT 3
}
OPTIONAL { ?id <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> ?v_1 . } .
OPTIONAL { ?id <http://www.w3.org/2000/01/rdf-schema#label> ?v_2 . }
}
ORDER BY DESC ( <LONG::IRI_RANK> (?id) )
In this way the limit works on the number of entities to fetch and not the number of solutions.
Best.
--
Andrea Giovanni Nuzzolese
Semantic Technology Laboratory (STLab)
Institute for Cognitive Science and Technology (ISTC)
National Research Council (CNR)
Via Nomentana 56, Roma - Itay
On Jun 13, 2011, at 6:47 PM, Rupert Westenthaler wrote:
> Hi Andrea, all
>
> While working on this I discovered something else:
>
> The "LIMIT" of SPARQL is based on solutions. For the Entityhub its
> semantic is that is defines the number of entities to select.
>
> When selecting multiple variables there is the possibility (actually
> it is very likely) that there are multiple solutions/entity. Therefore
> it can no longer be predicted how many entities are selected by a
> SPARQL query. This also affects CONSTRUCT queries as it will restrict
> the numbers of triples added to the resulting graph.
>
> Is if there is any possibility to work around this problem?
>
> best
> Rupert Westenthaler
>
> On Thu, Jun 9, 2011 at 3:57 PM, Andrea Giovanni Nuzzolese
> <nu...@cs.unibo.it> wrote:
>> The issue is STANBOL-222.
>>
>> Best.
>> Andrea
>>
>> On Jun 9, 2011, at 9:54 AM, Rupert Westenthaler wrote:
>>
>>> Hi
>>>
>>> Thx a lot. I was aware of the fact that optional constraints do cause
>>> this problem, but I have not known that rewriting the query like this
>>> can solve this problem.
>>> I will try to change the generation of SPARQL queries tomorrow on the
>>> way back from Berlin to Salzburg.
>>>
>>> would be nice if you could create a JIRA issue for that
>>>
>>> best
>>> Rupert
>>>
>>> On Wed, Jun 8, 2011 at 7:20 PM, Andrea Giovanni Nuzzolese
>>> <nu...@cs.unibo.it> wrote:
>>>> Hi,
>>>> I am trying to use the query service provided by the EntityHub.
>>>> The JSON field query I wrote is the following
>>>> {
>>>> "selected": ["http:\/\/www.w3.org\/2000\/01\/rdf-schema#label",
>>>> "http:\/\/www.w3.org\/1999\/02\/22-rdf-syntax-ns#type"],
>>>> "offset": "0",
>>>> "limit": "3",
>>>> "constraints": [
>>>> {
>>>> "type": "reference",
>>>> "field": "http:\/\/www.w3.org\/2002\/07\/owl#sameAs",
>>>> "value":
>>>> "http:\/\/www4.wiwiss.fu-berlin.de\/factbook\/resource\/United_States",
>>>> }]
>>>> }
>>>> and aims to find all the owl:sameAs entities of the entity
>>>> <http://www4.wiwiss.fu-berlin.de/factbook/resource/United_States> in
>>>> DBpedia.
>>>> But instead of the graph with the expected results I always receive the
>>>> error
>>>> javax.ws.rs.WebApplicationException:
>>>> org.apache.stanbol.entityhub.servicesapi.site.ReferencedSiteException:
>>>> Unable execute Query on remote site http://dbpedia.org/sparql
>>>> The sparql construct serialized by the EntityHub is the following
>>>> CONSTRUCT {
>>>> ?id <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> ?v_1 .
>>>> ?id <http://www.w3.org/2000/01/rdf-schema#label> ?v_2 .
>>>> <http://www.iks-project.eu/ontology/rick/query/QueryResultSet>
>>>> <http://www.iks-project.eu/ontology/rick/query/queryResult> ?id .
>>>> }
>>>> WHERE {
>>>> { {?id <http://www.w3.org/2002/07/owl#sameAs>
>>>> <http://www4.wiwiss.fu-berlin.de/factbook/resource/United_States> }}
>>>> { OPTIONAL { ?id <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> ?v_1 . }
>>>> }
>>>> { OPTIONAL { ?id <http://www.w3.org/2000/01/rdf-schema#label> ?v_2 . } }
>>>> }
>>>> ORDER BY DESC ( <LONG::IRI_RANK> (?id) ) LIMIT 3
>>>> If you try to run this construct directly on the SPARQL endpoint of dbpedia
>>>> the response is always "Virtuoso 42000 Error The estimated execution time 0
>>>> (sec) exceeds the limit of 1500 (sec)."
>>>> It seems that the problem is in the graph patterns containing optional as
>>>> they are bound to the whole default graph ( {OPTIONAL{triple pattern} } is
>>>> equivalent to { {} OPTIONAL {triple pattern} }.
>>>> In fact the query works properly both if you substitute the three graph
>>>> patterns into one graph pattern as follows
>>>> ...
>>>> WHERE {
>>>> ?id <http://www.w3.org/2002/07/owl#sameAs>
>>>> <http://www4.wiwiss.fu-berlin.de/factbook/resource/United_States> .
>>>> OPTIONAL { ?id <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> ?v_1 . }
>>>> OPTIONAL { ?id <http://www.w3.org/2000/01/rdf-schema#label> ?v_2 . }
>>>> }
>>>> ...
>>>>
>>>> and if you bind the optional to the global solution of the WHERE clause,
>>>> i.e.
>>>> ...
>>>> WHERE {
>>>> {{?id <http://www.w3.org/2002/07/owl#sameAs>
>>>> <http://www4.wiwiss.fu-berlin.de/factbook/resource/United_States> . }}
>>>> OPTIONAL { ?id <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> ?v_1 . } .
>>>> OPTIONAL { ?id <http://www.w3.org/2000/01/rdf-schema#label> ?v_2 . }
>>>> }
>>>> ...
>>>>
>>>>
>>>> Regards.
>>>> --
>>>> Andrea Giovanni Nuzzolese
>>>> Semantic Technology Laboratory (STLab)
>>>> Institute for Cognitive Science and Technology (ISTC)
>>>> National Research Council (CNR)
>>>> Via Nomentana 56, Roma - Itay
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>
>>>
>>>
>>> --
>>> | Rupert Westenthaler rupert.westenthaler@gmail.com
>>> | Bodenlehenstraße 11 ++43-699-11108907
>>> | A-5500 Bischofshofen
>>
>> --
>> Andrea Giovanni Nuzzolese
>> Semantic Technology Laboratory (STLab)
>> Institute for Cognitive Science and Technology (ISTC)
>> National Research Council (CNR)
>> Via Nomentana 56, Roma - Itay
>>
>>
>>
>>
>>
>>
>>
>
>
>
> --
> | Rupert Westenthaler rupert.westenthaler@gmail.com
> | Bodenlehenstraße 11 ++43-699-11108907
> | A-5500 Bischofshofen
Re: SPARQL serialization of FieldQuery
Posted by Rupert Westenthaler <ru...@gmail.com>.
Hi Andrea, all
While working on this I discovered something else:
The "LIMIT" of SPARQL is based on solutions. For the Entityhub its
semantic is that is defines the number of entities to select.
When selecting multiple variables there is the possibility (actually
it is very likely) that there are multiple solutions/entity. Therefore
it can no longer be predicted how many entities are selected by a
SPARQL query. This also affects CONSTRUCT queries as it will restrict
the numbers of triples added to the resulting graph.
Is if there is any possibility to work around this problem?
best
Rupert Westenthaler
On Thu, Jun 9, 2011 at 3:57 PM, Andrea Giovanni Nuzzolese
<nu...@cs.unibo.it> wrote:
> The issue is STANBOL-222.
>
> Best.
> Andrea
>
> On Jun 9, 2011, at 9:54 AM, Rupert Westenthaler wrote:
>
>> Hi
>>
>> Thx a lot. I was aware of the fact that optional constraints do cause
>> this problem, but I have not known that rewriting the query like this
>> can solve this problem.
>> I will try to change the generation of SPARQL queries tomorrow on the
>> way back from Berlin to Salzburg.
>>
>> would be nice if you could create a JIRA issue for that
>>
>> best
>> Rupert
>>
>> On Wed, Jun 8, 2011 at 7:20 PM, Andrea Giovanni Nuzzolese
>> <nu...@cs.unibo.it> wrote:
>>> Hi,
>>> I am trying to use the query service provided by the EntityHub.
>>> The JSON field query I wrote is the following
>>> {
>>> "selected": ["http:\/\/www.w3.org\/2000\/01\/rdf-schema#label",
>>> "http:\/\/www.w3.org\/1999\/02\/22-rdf-syntax-ns#type"],
>>> "offset": "0",
>>> "limit": "3",
>>> "constraints": [
>>> {
>>> "type": "reference",
>>> "field": "http:\/\/www.w3.org\/2002\/07\/owl#sameAs",
>>> "value":
>>> "http:\/\/www4.wiwiss.fu-berlin.de\/factbook\/resource\/United_States",
>>> }]
>>> }
>>> and aims to find all the owl:sameAs entities of the entity
>>> <http://www4.wiwiss.fu-berlin.de/factbook/resource/United_States> in
>>> DBpedia.
>>> But instead of the graph with the expected results I always receive the
>>> error
>>> javax.ws.rs.WebApplicationException:
>>> org.apache.stanbol.entityhub.servicesapi.site.ReferencedSiteException:
>>> Unable execute Query on remote site http://dbpedia.org/sparql
>>> The sparql construct serialized by the EntityHub is the following
>>> CONSTRUCT {
>>> ?id <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> ?v_1 .
>>> ?id <http://www.w3.org/2000/01/rdf-schema#label> ?v_2 .
>>> <http://www.iks-project.eu/ontology/rick/query/QueryResultSet>
>>> <http://www.iks-project.eu/ontology/rick/query/queryResult> ?id .
>>> }
>>> WHERE {
>>> { {?id <http://www.w3.org/2002/07/owl#sameAs>
>>> <http://www4.wiwiss.fu-berlin.de/factbook/resource/United_States> }}
>>> { OPTIONAL { ?id <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> ?v_1 . }
>>> }
>>> { OPTIONAL { ?id <http://www.w3.org/2000/01/rdf-schema#label> ?v_2 . } }
>>> }
>>> ORDER BY DESC ( <LONG::IRI_RANK> (?id) ) LIMIT 3
>>> If you try to run this construct directly on the SPARQL endpoint of dbpedia
>>> the response is always "Virtuoso 42000 Error The estimated execution time 0
>>> (sec) exceeds the limit of 1500 (sec)."
>>> It seems that the problem is in the graph patterns containing optional as
>>> they are bound to the whole default graph ( {OPTIONAL{triple pattern} } is
>>> equivalent to { {} OPTIONAL {triple pattern} }.
>>> In fact the query works properly both if you substitute the three graph
>>> patterns into one graph pattern as follows
>>> ...
>>> WHERE {
>>> ?id <http://www.w3.org/2002/07/owl#sameAs>
>>> <http://www4.wiwiss.fu-berlin.de/factbook/resource/United_States> .
>>> OPTIONAL { ?id <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> ?v_1 . }
>>> OPTIONAL { ?id <http://www.w3.org/2000/01/rdf-schema#label> ?v_2 . }
>>> }
>>> ...
>>>
>>> and if you bind the optional to the global solution of the WHERE clause,
>>> i.e.
>>> ...
>>> WHERE {
>>> {{?id <http://www.w3.org/2002/07/owl#sameAs>
>>> <http://www4.wiwiss.fu-berlin.de/factbook/resource/United_States> . }}
>>> OPTIONAL { ?id <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> ?v_1 . } .
>>> OPTIONAL { ?id <http://www.w3.org/2000/01/rdf-schema#label> ?v_2 . }
>>> }
>>> ...
>>>
>>>
>>> Regards.
>>> --
>>> Andrea Giovanni Nuzzolese
>>> Semantic Technology Laboratory (STLab)
>>> Institute for Cognitive Science and Technology (ISTC)
>>> National Research Council (CNR)
>>> Via Nomentana 56, Roma - Itay
>>>
>>>
>>>
>>>
>>>
>>>
>>
>>
>>
>> --
>> | Rupert Westenthaler rupert.westenthaler@gmail.com
>> | Bodenlehenstraße 11 ++43-699-11108907
>> | A-5500 Bischofshofen
>
> --
> Andrea Giovanni Nuzzolese
> Semantic Technology Laboratory (STLab)
> Institute for Cognitive Science and Technology (ISTC)
> National Research Council (CNR)
> Via Nomentana 56, Roma - Itay
>
>
>
>
>
>
>
--
| Rupert Westenthaler rupert.westenthaler@gmail.com
| Bodenlehenstraße 11 ++43-699-11108907
| A-5500 Bischofshofen