Hi Barry,
I don't understand the assembler syntax enough to directly help (no
doubt others can) but given you didn't get any error messages when you
had the wrong URI then not getting an error message from "bla" isn't
definitive :)
As mentioned your other alternative is to leave the reasoner in hybrid
mode and write your rules in backward syntax.
Dave
On 19/01/18 09:49, Nouwt, B. (Barry) wrote:
Hi all,
I fixed the error Dave found, but it does not seem to activate
‘backward’ mode. I test it by providing a wrong value ‘bla’ instead of
‘backward’ and check whether Fuseki fails to load the assembler. But,
unfortunately, it doesn’t fail.
Any other suggestions on how to enable ‘backward’ mode from an assembler
file?
Regards, Barry
Verzonden vanaf mijn Windows 10-telefoon
*Van: *Dave Reynolds <mailto:[email protected]>
*Verzonden: *donderdag 18 januari 2018 09:40
*Aan: *[email protected] <mailto:[email protected]>
*Onderwerp: *Re: GenericRuleReasoner with limited scope
Hi Barry,
I'm not sure of the assembler syntax but there's one error in your
example which might fix it:
> @prefix rr: <http://jena.hpl.hp.com/2003/RuleReasoner> .
That should be:
@prefix rr: <http://jena.hpl.hp.com/2003/RuleReasoner#> .
Dave
On 17/01/18 15:12, Nouwt, B. (Barry) wrote:
Hi Dave, thanks for the answer.
I was not aware that the backward reasoner started at triple patterns
(retrieved from the SPARQL query), so I will definitely test whether that
indeed causes the rule to be applied once instead of twice in the example
described in my second post.
My setup uses Apache Jena Fuseki, so the PROPruleMode should be configured via a assembly TTL file. Do you know how to do that? I found the 'http://jena.hpl.hp.com/2003/RuleReasoner/ruleMode' property in the
ReasonerVocabulary.java file [1], but it does not seem to load this
property when I use the following assembly:
@prefix rr: <http://jena.hpl.hp.com/2003/RuleReasoner> .
.
.
.
<#infGraph> rdf:type ja:InfModel ;
ja:reasoner [ ja:rulesFrom <file:src/test/resources/et.rules> ;
rr:ruleMode "backward" ; ] ;
ja:content <#test-inf> .
Any pointers are welcome!
Regards, Barry
[1]
https://github.com/apache/jena/blob/cc038809fb622779933831011909714e22ef494c/jena-core/src/main/java/org/apache/jena/vocabulary/ReasonerVocabulary.java#L77
-----Original Message-----
From: Dave Reynolds [mailto:[email protected]]
Sent: woensdag 17 januari 2018 09:33
To: [email protected]
Subject: Re: GenericRuleReasoner with limited scope
On 16/01/18 09:55, Nouwt, B. (Barry) wrote:
Hi everyone,
Currently I'm using the GenericRuleReasoner of Apache Jena in my project to
apply custom rules to my RDF data. This works as expected: as soon as I execute
the first SPARQL query in Apache Jena Fuseki, the GenericRuleReasoner correctly
determines all the derived triples and the query can be answered.
Now I am looking for the following GenericRuleReasoner (or another reasoner)
behavior:
1. I would like the GenericRuleReasoner to take the SPARQL query into
account when reasoning. So, only reason about those facts that 'seem' relevant
for answering the SPARQL query.
2. I would like the GenericRuleReasoner to remove the derived triples
after the SPARQL query has been answered. So, the next time it receives the
same SPARQL query, it will not be able to reuse the previous reasoning result.
If I understand what you want then use the backward rather than forward engine.
The GenericRuleReasoner contains two engines which can be used separately or in
a cascade (hybrid mode). For configuring this see PROPruleMode in
https://jena.apache.org/documentation/inference/#RULEconfiguration
The backward reasoner is driven by goals at the level of triple patterns and
isn't aware of the overall sparql query so the goals are not very selective but
it will at least help with point #1.
In terms of point #2 then the backward engine, by default, will not retain any
answers. You can use the tabling declarations to cause it to selectively
remember the answer to specific (sub)goals if you need to see:
https://jena.apache.org/documentation/inference/#RULEbackward
Note that in hybrid mode (the default) you can still use backward rules by
writing them with the arrow reversed. The advantage of switching the reasoner
mode is that you can use the same rule source syntax and run the rules in
either forward or backward mode to test the difference.
Dave
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