Hi Lorenz, Thank you for your answer.
Quick follow up. I think the issue for me is the documentation of the built-ins is too abstract or relies on understanding the source code. So I suppose, documentation / tutorial seems somewhat superfluous when you can do that – only I can’t understand what’s there and the source at the moment. 1. Yes, I seem to understand difference is a no go but I was wondering if there might be some work around coercing the dateTime to something else. I’m not sure I understood that very well but it looks like I can’t use functions in arguments of built-ins (so no xsd:year(?date) or whatever). But then, on greaterThan, something should be workable if I have xsd:dateTime, no? What’s wrong with : [ruleMissedDeadline2: (?conference ns:hasDeadline ?date) now(?now) greaterThan(?now, ?date) -> (?conference ns:status ns:DeadlinePassed) ] 2. When you say extend the rule system, you mean adding a class using as a starting point something is in ..rulesys.builtins and adapting it and then rebuild all the jars. I’m using Fuseki, so I’d have to rebuild that too, yeah? Aside from the fact I’m not coding in java, this isn’t the easiest path for me at the moment. Many thanks, Pierre From: Lorenz B. [mailto:[email protected]] Sent: 16 May 2019 08:33 To: [email protected] Subject: Re: Documentation/tutorial on using dates in Jena rules with GenericRuleReasoner I'm not aware of any tutorial, but afaik you can't do what you did here with SPARQL in Jena rules without writing custom built-ins or by extending the existing ones because: * the "difference" built-in does only work for numbers right now [1] * there is no support for duration type at all it looks like So, so far you could only compare datetime values via lessThan, le, greaterThan, ge but there is no other built-in with support for date values so far. Others might indeed correct me if I'm wrong of. It looks like, you have to extend the rule system by custom built-ins - it's not that difficult though [2] [1] https://github.com/apache/jena/blob/master/jena-core/src/main/java/org/apache/jena/reasoner/rulesys/builtins/Difference.java#L68<https://github.com/apache/jena/blob/master/jena-core/src/main/java/org/apache/jena/reasoner/rulesys/builtins/Difference.java#L68> [2] https://jena.apache.org/documentation/inference/#builtins<https://jena.apache.org/documentation/inference/#builtins> > Could people recommend a good reference/tutorial on how to use built-ins > (greaterThan, difference, now etc) with dates (e.g., datetime, duration and > so on) in rules for the GenericRuleReasoner? > > Example: > > Assume a KB of conferences with their deadlines as xsd:dateTime. > > Here are examples of SPARQL queries to find conferences whose deadlines are > passed: > > SELECT * WHERE { > ?subject here:hasDeadline ?date . > BIND((xsd:dateTime(?date) - now()) AS ?Span) > FILTER(?Span < "P0D"^^xsd:duration) > } > > SELECT * WHERE { > ?subject here:hasDeadline ?date . > FILTER(now() > xsd:dateTime(?date)) > } > > Suppose instead I wanted to infer some attribute of the conference, e.g: > > ?subject here:hasStatus here:DeadlinePassed > > I don't really get how to do that in a rule and I can't quite figure if I'm > misusing the built-ins or just mixing SPARQL and rule syntax (e.g., when > trying to coerce variables to datatypes). > > There's a bunch of recurring questions around that sort of rules but I can't > quite find any answer that's giving clear examples. > > Thus I would find it useful if anybody could point at a resource that goes > through some sort of how to do date comparison and use that in rules as the > Jena doc on built-in is not self-contained in that respect. > > https://jena.apache.org/documentation/inference/#rules<https://jena.apache.org/documentation/inference/#rules> > > > With many thanks and kind regards, > Pierre > -- Lorenz Bühmann AKSW group, University of Leipzig Group: http://aksw.org<http://aksw.org> - semantic web research center THIS E-MAIL MAY CONTAIN CONFIDENTIAL AND/OR PRIVILEGED INFORMATION. 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