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Posted by lhwong at Nov 23, 2006 6:02:42 AM

Tolog for RDF
Have done an experimental version of Tolog for querying RDF statements stored in a Sesame repository.
http://www.geocities.com/burunghelang/sesame.zip
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Grammar.txt (1157 bytes) (Download Count: 534) (Grammar)

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Test.txt (4606 bytes) (Download Count: 1512) (Test)

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mem-rdf1.rdf (41765 bytes) (Download Count: 976) (Test 1)

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mem-rdf2.zip (4010 bytes) (Download Count: 603) (Test repository 2)

Posted by jeen at Nov 24, 2006 9:10:00 AM

Re: Tolog for RDF
This sounds very interesting. Unfortunately the link you gave does not seem to work.

Can you give a few more details about what exactly you have done? Have you implemented a Tolog engine on top of Sesame, or have you taken an existing Tolog implementation and somehow 'coupled' it with Sesame?
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Researcher at AFSG - Wageningen UR

Posted by lhwong at Nov 24, 2006 9:23:42 AM

Re: Tolog for RDF

This sounds very interesting. Unfortunately the link you gave does not seem to work.

Have tested the link to be ok. Please try typing the full URL in the browser instead of clicking on the link. May be it is the download limit set by the host site. Unfortunately the file size is more than 2Mb so I cannot attach it here.

Can you give a few more details about what exactly you have done?

This is a course assignment that I did for a second semester elective subject in a Master degree course at ISS (http://iss.nus.edu.sg). It is a proof of concept project that shows that Tolog can be implemented as a query language for RDF.

Have you implemented a Tolog engine on top of Sesame, or have you taken an existing Tolog implementation and somehow 'coupled' it with Sesame?

The Tolog parser and engine are implemented on top of Sesame. The Tolog parser and engine extends the codes from Steve Metsker's book "Building Parsers with Java".

Posted by olivo_miotto at Feb 9, 2007 5:34:14 AM

Re: Tolog for RDF
Hi jeen

it was one of my students who posted that link.
You can email me if you want additional info.

The tolog implementation was done by adding the engine code inn a package org.openrdf.sesame.query.tolog. The resulting customized version of Sesame has tolog as a query language alongside the rest.

The engine requires the "Building Parsers with Java" class library.

Since this was a module project, I believe the students will not be actively developing this code. You're welcome to it though. I can say that it seems to be working properly. Let me know if you need anything else.

Best regards
Olivo Miotto
olivo@iss.nus.edu.sg
National university of Singapore

This sounds very interesting. Unfortunately the link you gave does not seem to work.

Can you give a few more details about what exactly you have done? Have you implemented a Tolog engine on top of Sesame, or have you taken an existing Tolog implementation and somehow 'coupled' it with Sesame?

Posted by lhwong at Mar 5, 2007 6:20:27 AM

Re: Tolog for RDF
Uploaded Tolog for RDF project source at http://www.geocities.com/burunghelang/sesame-1.2.5.zip.

Posted by lhwong at Mar 9, 2007 4:08:58 AM

Re: Tolog for RDF
Uploaded Tolog for RDF source at http://burunghelang.googlepages.com/sesame-1.2.5.zip

Posted by jeen at Mar 9, 2007 10:44:55 AM

Re: Tolog for RDF
Very cool!

I've played with it a little bit and I very much like the notion of including this in Sesame somehow. The fact that you can formulate adhoc inference rules (in a prolog-like fashion) seems very powerful.

Of course, there are plenty of questions and issues still (scalability, safety of the language, etc., as well as a number of problems with the grammar and parsing that I ran into). I plan to take a closer look at exactly how you implemented this later.

What exactly are your plans with this code? Do you plan to keep working on improving it?
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Researcher at AFSG - Wageningen UR

Posted by lhwong at Mar 9, 2007 11:27:47 AM

Re: Tolog for RDF

Very cool!

Thanks for your kind appreciation.

I've played with it a little bit and I very much like the notion of including this in Sesame somehow.

Cool!

The fact that you can formulate adhoc inference rules (in a prolog-like fashion) seems very powerful.

The query language is like the marriage between Datalog and SQL.

Of course, there are plenty of questions and issues still (scalability, safety of the language, etc., as well as a number of problems with the grammar and parsing that I ran into). I plan to take a closer look at exactly how you implemented this later.

Yes, I agree with you there are issues outstanding like:-

- there is not enough error handling in the parser codes.
- the parser codes are inefficient.
- there is the danger of indefinite recursion in the query execution engine codes.
- the query execution engine codes are inefficient.
- the query language grammar is not complete.

What exactly are your plans with this code? Do you plan to keep working on improving it?

I am not open source savvy and don't really know how to participate in the further development of the codes. If given the chance to work on improving it, I would very much like to participate in the process.