Forking a thread off to dev@:
Do we have a global policy about where null is accepted as a wildcard? I know
it works in at least some places...
I would love to (over an appropriate period of time and with lots of warnings
and deprecation and so forth) stop letting it be a wildcard and require code to
use the actual wildcard objects.
ajs6f
> On May 8, 2018, at 11:51 AM, Andy Seaborne <a...@apache.org> wrote:
>
> Barry,
>
> As a general concept "matching" happens at different levels.
>
> Triple.match corresponds to the matching done by Graph.find - RDF terms (URI,
> bnode, literal) match exactly, and Node.ANY is a wildcard.
>
> Triple t1 = Triple.ANY;
> Triple t2 = SSE.parseTriple("(:s :p :o)");
> t1.matches(t2) -> true
> t2.matches(t1) -> false
>
> Variables are a concept for SPARQL - and matches usefully need to return
> which variable matched which RDF Term.
>
> Triple patterns match against graphs and return an iterator of ways they
> match.
>
> Consider cases like "?x ?p ?x" where the variables impose am additional shape.
>
> If you want variable bindings, you could build a SPARQL query or wrap up some
> of the internal code e.g.
>
> /** Evaluate a triple pattern */
> private static QueryIterator match(Graph source, Triple pattern) {
> ExecutionContext execContext =
> new ExecutionContext(ARQ.getContext(), source, null, null) ;
> QueryIterator chain = QueryIterRoot.create(execContext)
> chain = new QueryIterTriplePattern(chain, pattern, execContext) ;
> return chain ;
> }
>
> Andy
>
> On 08/05/18 09:21, Nouwt, B. (Barry) wrote:
>> Hi everybody,
>> I’m trying to reuse Apache Jena code that parses and matches triples. I’m
>> currently looking at the SSE class’s parseTriple() method. This seems to fit
>> my purpose for parsing a string representation of a triple into a triple
>> object. I also noticed the following Javadoc on the Node.maches(Node) method:
>> Answer true iff this node accepts the other one as a match.
>> The default is an equality test; it is over-ridden in subclasses to
>> provide the appropriate semantics for literals, ANY, and variables.
>> Since this is exactly what I’m looking for, I’ve tried to match two triples
>> using the matches() method, but it does not seem to work:
>> Triple t1 = SSE.parseTriple("(?s ?p ?o)");
>> Triple t2 = SSE.parseTriple("(test:subject test:predicate test:object)", pm);
>> t1.matches(t2)
>> The final statement returns false, while I would expect it to return true.
>> Either, I’m missing something (which is completely realistic 😊), or I should
>> use some other method to match two triples in the way described above.
>> Any help is appreciated!
>> Regards, Barry
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