On 29/10/12 16:31, John Liu wrote:
Thank you very much Andy for your quick action.
It will be in tonight's snapshot build of 2.7.5-SNAPSHOT (it builds at about
05:00 UTC)
When will Jena 2.7.5 be released?
We have just release 2.7.4 so not immediately.
We do, as a project, practice de facto, "green trunk" i.e. the trunk is
in a state to be released (svn code trunk and nightly build, which is a
build of trunk). The code even stamps the exact snapshot build and
build timestamp to identify precisely which code it is.
Not all algebra expressions can be turned into a query. If you are
manipulating the algebra, you can create forms OpAsQuery does not recognize.
Can I assume that all ops which are compiled from a sparql query can
be turned back to a sparql query? For example, the following codes are
always working fine:
Yes but test. The idea is any valid query will be reversed into an
equivalent query (equivalent => same answers ; it may not test .equals
with the input - surface details have been lost in the algebra). It is
a pragmatic reconstruction of an equivalent query, not a theoretically
proven process.
AlgebraGenerator ag = new AlgebraGenerator();
Op op = ag.compile(query);
Op op = Algebra.compile(query) ;
Query query2 = OpAsQuery.asQuery(op);
The reason why we use these functions is that we want to add filters
into the query in runtime, for example modifying the op by adding a
filter expression (op = OpFilter.filter(e, op);), is this the best
way to do that(adding a filter)?
Do you need to turn it back into query syntax? You can directly execute
the algebra after modification.
Andy
Thanks, John
________________________________
From: Andy Seaborne <[email protected]>
To: [email protected]
Sent: Friday, October 26, 2012 6:19:00 PM
Subject: Re: ARQNotImplemented exception thrown by ARQ function calls
Oversight - I've just implemented it (it's not hard!). It wil be in
tonight's snapshot build of 2.7.5-SNAPSHOT (it builds at about 05:00 UTC)
https://repository.apache.org/content/repositories/snapshots/org/apache/jena/apache-jena/
By the way, you can execute algebra expressions directly:
DatasetGraph dsg = ...
QueryIterator qIter = Algebra.exec(op, dsg) ;
Not all algebra expressions can be turned into a query. If you are
manipulating the algebra, you can create forms OpAsQuery does not recognize.
Andy
On 26/10/12 22:24, John Liu wrote:
I use some Jena arq apis to modify the query for adding filter in runtime.
The query is
PREFIX geo: <http://www.w3.org/2003/01/geo/wgs84_pos#>
PREFIX onto: <http://dbpedia.org/ontology/>
SELECT * WHERE {
?p a onto:Place .
?p geo:l* ?loc .
}
There is valid card in the line "?p geo:l* ?loc ."
The funcations I used are:
AlgebraGenerator ag = new AlgebraGenerator();
Op op = ag.compile(query);
op = OpFilter.filter(e, op);
Query query2 = OpAsQuery.asQuery(op);
This query causes an ARQNotImplemented exception thrown in the last function
call. The exception stack trace is:
com.hp.hpl.jena.sparql.ARQNotImplemented error occurred when handling the REST
data service.
Not implemented: OpPath
at
com.hp.hpl.jena.sparql.algebra.OpAsQuery$Converter.visit(OpAsQuery.java:224)
at com.hp.hpl.jena.sparql.algebra.op.OpPath.visit(OpPath.java:73)
at
com.hp.hpl.jena.sparql.algebra.OpAsQuery$Converter.asElementGroup(OpAsQuery.java:97)
at
com.hp.hpl.jena.sparql.algebra.OpAsQuery$Converter.asElement(OpAsQuery.java:88)
at
com.hp.hpl.jena.sparql.algebra.OpAsQuery$Converter.visit(OpAsQuery.java:168)
at com.hp.hpl.jena.sparql.algebra.op.OpSequence.visit(OpSequence.java:75)
at
com.hp.hpl.jena.sparql.algebra.OpAsQuery$Converter.visit(OpAsQuery.java:473)
at com.hp.hpl.jena.sparql.algebra.op.OpSlice.visit(OpSlice.java:50)
at
com.hp.hpl.jena.sparql.algebra.OpAsQuery$Converter.asElementGroup(OpAsQuery.java:97)
at
com.hp.hpl.jena.sparql.algebra.OpAsQuery$Converter.asElement(OpAsQuery.java:88)
at
com.hp.hpl.jena.sparql.algebra.OpAsQuery$Converter.visit(OpAsQuery.java:310)
at com.hp.hpl.jena.sparql.algebra.op.OpFilter.visit(OpFilter.java:110)
at com.hp.hpl.jena.sparql.algebra.OpAsQuery.asQuery(OpAsQuery.java:50)
The arq library I used is jena-arq-2.9.1 and the jean is jena-core-2.7.1
My question is if this is bug in the arq functions? I have tested these
functions without adding the filter(the third call), but it still throws the
exception.
If it isa bug, how can I file a defect to it?
If it is not, how can I fix my code to avoid this exception.
Thanks a lot for your help.
John
