I have create an endpoint SPAQL on OpenLink Virtuoso.
All work well, but i have to access on the data in a Container, in particular a rdf:Seq.
I have a Seq like this:
<myrdf:has_stoptimes>
<rdf:Seq rdf:about="http://test.com/343">
<rdf:li>
<myrdf:StopTime rdf:about="http://test.com/StopTime/434">
...
</ns0:StopTime>
</rdf:li>
<rdf:li>
<myrdf:StopTime rdf:about="http://test.com/StopTime/435">
...
</ns0:StopTime>
</rdf:li>
</rdf:Seq>
Now i see that to access data in a container i can use rdfs:member or FILTER (strstarts(str(?prop), str(rdf:_)) how is explained here
But for my project i have to adopt the first solution because i'm working with Silk and i will use the code syntax like ?a/myrdf:has_stoptimes/rdfs:member without use of "complex" filter.
I have tried to follow this guide but querying the endpoint nothing work how i hoped.
So my question is: how can i query ?a/myrdf:has_stoptimes/rdfs:member on a Virtuoso endpoint SPARQL?Which inference rule i have to add in endpoint SPARQL?
Thank you in advance
UPDATE
I have created the following inference rules in Virtuoso:
ttlp (' #prefix rdfs: .
#prefix rdf: .
rdfs:Container rdf:type rdfs:Class ; rdfs:subClassOf rdfs:Resource .
rdfs:ContainerMembershipProperty a rdfs:Class ; rdfs:subClassOf rdf:Property .
rdf:Seq rdf:type rdfs:Class ; rdfs:subClassOf rdfs:Container .
rdfs:member rdf:type rdf:Property ; rdfs:domain rdfs:Resource ; rdfs:range rdfs:Resource .
', '', 'http://localhost:8890/schema/test') ;
Nothing work querying the SPARQL endpoint like:
define input:inference "http://localhost:8890/schema/property_rules1"
SELECT *
FROM
WHERE {?sep a rdf:Seq.
?seq rdfs:member ?p}
After i tried adding the follow line to the ttl file: rdf:_1 rdfs:subPropertyOf rdfs:member . In this way it work but obviously the results are only for the first element of the container. So is very unconvenient add a line for all of rdf:_n, and i think this is only a temporary solution, it is not correct.
I have tried to add an RDF dump on SILK 2.6.1, and on the section SPARQL of the data source if i run the query:
SELECT *
FROM
WHERE {?sep a rdf:Seq.
?seq rdfs:member ?p}
I obtain the correct result, without specify any inference rules. So i think that in this functionality of SILK there is something that i’m missing in my endpoint SPARQL or am i saying nonsense things?
You can't use variables in property paths, so you can't actually do
?x ?a/has_stoptimes/rdfs:member ?y
Instead, you have to use another variable or blank node in between:
?x ?a ?z . ?z has_stoptimes/rdfs:member ?y
?x ?a [ has_stoptimes/rdfs:member ?y ] .
Related
I am using the RDFS-Plus (Optimized) ruleset. According to this: https://docs.cambridgesemantics.com/anzograph/v2.2/userdoc/inferences.htm
If something is of type owl:Class it should be inferred it is an rdfs:subClassof owl:Thing.
If I run the query
PREFIX owl: <http://www.w3.org/2002/07/owl#>
select ?s ?p where {
?s ?p owl:Thing .
}
I only get results for when I have explicitly stated that a class is an rdfs:subClassOf owl:Thing
Can someone explain what I am missing and why this does not seem to work as expected?
I looked at the .pie rule files located in $GDB_HOME/configs/rules and found that the graphdb rulesets do not match the link in the question. The least complex ruleset (according to https://graphdb.ontotext.com/documentation/free/rules-optimisations.html#hints-on-optimizing-graphdb-s-rulesets) that provides the functionality needed is owl2-ql-optimized.
I'm trying to get my head around inferring RDF data. Say that I have these triples (RDF Turtle), which I created using Protege:
#prefix owl: <http://www.w3.org/2002/07/owl#> .
#prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> .
:hasSpouse rdf:type owl:ObjectProperty ,
owl:SymmetricProperty ;
rdfs:domain :People ;
rdfs:range :People .
:People rdf:type owl:Class .
:Jane_Doe rdf:type owl:NamedIndividual ,
:People .
:John_Doe rdf:type owl:NamedIndividual ,
:People ;
:hasSpouse :Jane_Doe .
The reasoner in Protege will kindly highlight the expected inference, that is :Jane_Doe :hasSpouse :John_Doe.
How can I see that inference with SPARQL? If I run this query in Protege (SPARQL tab):
SELECT ?subject
WHERE {?subject hasSpouse ?object .}
It shows the asserted triple, not the inferred one. I understand how to do it manually, e.g. :
CONSTRUCT {?object ?prop ?subject }
WHERE { ?prop rdf:type owl:SymmetricProperty .
?subject ?prop ?object .}
I'd see now the inferred data I'm expecting but 1) that would be losing the point imho (i.e; reinventing the wheel) 2) I cannot have 2 queries in this tab (construct, then select). There's got to be a way to do this automatically, just like the reasoner did.
I read in Stack Overflow a post saying to use 'Snap SPARQL' plugin in Protege. I tried but simple queries don't work (like the first one above). It's like it's a different language. How does it work?
So, how can I get the benefit of these owl properties with SPARQL? How can I have an OWL-aware SPARQL in Protege? Am I taking this the wrong way? What's the right way?
thanks for your help.
Nicolas
You need to make your inferences a part of your knowledge.
To do so, go to the SWRL Tab and click successively on the button
at the bottom of that Tab, start from the left to the right.
Is it possible to execute SPARQL construct while adding information outside the scope of query? e.g., I want to execute SPARQL construct while defining enumeration information like this:
PREFIX skos:<http://www.w3.org/2004/02/skos/core#>
construct {
?s a skos:Concept
?s ex:index <enumeration starting from 1 -- this is just a sample>
}
where {
?s a skos:Concept
}
is it possible to do something like that with pure SPARQL? what are the alternatives?
* Additional Information *
Probably I am not explained my problem clearly, so basically I want to achieve the following (assuming that ex:index is a valid datatypeProperty):
== Initial RDF triples ==
#prefix skos:<http://www.w3.org/2004/02/skos/core#>
#prefix ex: <http://example.org/> .
ex:abc rdf:type skos:Concept .
ex:def rdf:type skos:Concept .
...
ex:endOfSample rdf:type skos:Concept .
== RDF triples after SPARQL Update execution ==
#prefix skos:<http://www.w3.org/2004/02/skos/core#>
#prefix ex: <http://example.org/> .
ex:abc rdf:type skos:Concept ;
ex:index 1 .
ex:def rdf:type skos:Concept ;
ex:index 2 .
...
ex:endOfSample rdf:type skos:Concept ;
ex:index <endOfSampleNumber> .
You can construct any valid RDF value in a CONSTRUCT. However the query will fail if any of the variables in the CONSTRUCT graph pattern is unbound after executing the WHERE graph. I.e. there can be no binding for ?p in your query and the CONSTRUCT will never execute.
This is an example that should get you started:
PREFIX skos:<http://www.w3.org/2004/02/skos/core#>
PREFIX ex:<http://example.org/construct#>
construct {
ex:someProp a owl:ObjectProperty .
?s ex:someProp (1 2 3)
}
where {
?s a skos:Concept
}
This will result in the construction of seven triples for the property value and the list structure.
The ex:someProp is added because there isn't a good object property in SKOS for ad-hoc lists. It would be best to define the property with some semantic meaning. Also note that while the {ex:someProp a owl:ObjectProperty} triple will be asserted for each match of {?s a skos:Concept}, it is the same triple, hence there will be only one in the end. The price is efficiency, so asserting the property outside of this query would be a better choice - it is included in the above query for the sake of example completeness.
I have an OWL file that includes a taxonomic hierarchy that I want to write a query where the answer includes each individual and its immediate taxonomic parent. Here's an example (the full query is rather messier).
#prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#> .
#prefix rdf: <http:://www.w3.org/1999/02/22-rdf-syntax-ns#> .
#prefix : <urn:ex:> .
:fido rdf:type :Dog .
:Dog rdfs:subClassOf :Mammal .
:Mammal rdfs:subClassOf :Vertebrate .
:Vertebrate rdfs:subClassOf :Animal .
:fido :hasToy :bone
:kitty rdf:type :Cat .
:Cat rdfs:subClassOf :Mammal .
:kitty :hasToy :catnipMouse .
And this query does what I want.
prefix rdf: <http:://www.w3.org/1999/02/22-rdf-syntax-ns#> .
prefix : <urn:ex:> .
SELECT ?individual ?type
WHERE {
?individual :hasToy :bone .
?individual rdf:type ?type .
}
The problem is that I'd rather use a reasoned-over version of the OWL file, which unsurprisingly includes additional statements:
:fido rdf:type :Mammal .
:fido rdf:type :Vertebrate .
:fido rdf:type :Animal .
:kitty rdf:type :Mammal .
:kitty rdf:type :Vertebrate .
:kitty rdf:type :Animal .
And now the query results in additional answers about Fido being a Mammal, etc. I could just give up on using the reasoned version of the file, or, since the SPARQL queries are called from java, I could do a bunch of additional queries to find the least inclusive type that appears. My question is whether there is a reasonable pure SPARQL solution to only returning the Dog solution.
A generic solution is that you make sure you ask for the direct type only. A class C is the direct type of an instance X if:
X is of type C
there is no C' such that:
X is of type C'
C' is a subclass of C
C' is not equal to C
(that last condition is necessary, by the way, because in RDF/OWL, the subclass-relation is reflexive: every class is a subclass of itself)
In SPARQL, this becomes something like this:
PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#>
PREFIX : <urn:ex:> .
SELECT ?individual ?type
WHERE {
?individual :hasToy :bone .
?individual a ?type .
FILTER NOT EXISTS { ?individual a ?other .
?other rdfs:subClassOf ?type .
FILTER(?other != ?type)
}
}
Depending on which API/triplestore/library you use to execute these queries, there may also be other, tool-specific solutions. For example, the Sesame API (disclosure: I am on the Sesame dev team) has the option to disable reasoning for the purpose of a single query:
TupleQuery query = conn.prepareTupleQuery(SPARQL, "SELECT ...");
query.setIncludeInferred(false);
TupleQueryResult result = query.evaluate();
Sesame also offers an optional additional inferencer (called the 'direct type inferencer') which introduces additional 'virtual' properties you can query, such as sesame:directType, sesame:directSubClassOf, etc. Other tools will undoubtedly have similar options.
I am doing some experiments with importing triples formulated in the turtle language
within the openrdf-workbench webapp in Tomcat, which has incorporated a SPARQL endpoint.
I wonder if with turtle, or, generally, in RDF / RDFS is it possible to add a certain predicate/object declaration on all (implicit) subjects conditionally to the existence of another predicate/object.
For example, if I have the following triples defined:
foo:a foo:b foo:c
foo:d foo:b foo:c
foo:e foo:b foo:c
foo:f foo:b foo:c
I would like to automatically add the following predicate/subject to all subjects that match predicate=foo:b and object=foo:c:
(implicit subject) foo:g foo:h
in order to automatically produce the following triples:
foo:a foo:g foo:h
foo:d foo:g foo:h
foo:e foo:g foo:h
foo:f foo:g foo:h
Is this possible?
Alternatively: is there any way to define some triples in order to enable SPARQL to find foo:a/d/e/f when queried for subjects that have foo:g foo:h as predicate/object?
Part 1 - Creating additional information
The first part of your question can be solved in one of two ways:
Using Inference
Using SPARQL Update
Inferencing
Inference is a technique whereby you define rules that infer additional triple based on your existing triples. You typically either use a pre-defined set of rules or use your own custom rules. I think Sesame only supports pre-defined rule sets out of the box so you may want to take a look at OWLIM which is an alternative back end that can be used with Sesame and has much more customisable rules AFAIK.
Inferencing can typically be applied in two ways, one where you only store the rules and you compute the additional information every time a rule fires and another where you pre-compute all the additional information and add it to your database. Which you will want to use depends on how you intend to use your system and there are performance trade offs involved. I'm not going into detail because that's really a whole other question - see Forward vs Backward Chaining for some discussion
SPARQL Update
Alternatively if your rules are relatively simple and you are OK with pre-computing the extra information and adding it to your database you can write SPARQL Updates to do this e.g.
PREFIX foo: <http://example.org/foo#>
INSERT
{
?x foo:g foo:h .
}
WHERE
{
?x foo:b foo:c .
}
Part 2 - Querying the Data
I am guessing you are fairly new to SPARQL because from what you've described this sounds trivial to me.
If I wanted to find all subjects which had the predicate foo:g and the object foo:h I would simply write the following:
PREFIX foo: <http://example.org/foo#>
SELECT ?x
WHERE
{
?x foo:g foo:h .
}
You can do this type of inference using OWL with an axiom of the form
p value a ⊑ q value b
which says that if something has a as a value for property p, then it also has b as a value for property q. As an example, here's an ontology with four individuals (a, b, c, d), two object properties (p, q), and the axiom (p value c ⊑ q value d).
#prefix : <http://example.org/add-predicate-object#> .
#prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#> .
#prefix owl: <http://www.w3.org/2002/07/owl#> .
#prefix xsd: <http://www.w3.org/2001/XMLSchema#> .
#prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> .
<http://example.org/add-predicate-object> a owl:Ontology .
:p a owl:ObjectProperty .
:q a owl:ObjectProperty .
[ a owl:Restriction ;
owl:onProperty :p ;
owl:hasValue :c ;
rdfs:subClassOf [ a owl:Restriction ;
owl:onProperty :q ;
owl:hasValue :d ] . ] .
:a a owl:Thing, owl:NamedIndividual ; :p :c .
:b a owl:Thing, owl:NamedIndividual ; :p :c .
:c a owl:Thing, owl:NamedIndividual .
:d a owl:Thing, owl:NamedIndividual .
In Protégé, the axiom looks like this:
You can enable a reasoner and query for instances of q value d and see:
or you can browse to individuals and see the results: