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Re: bringing ShEx and Shacl closer

From: Eric Prud'hommeaux <eric@w3.org>
Date: Tue, 15 Mar 2016 06:02:33 -0400
To: Iovka Boneva <iovka.boneva@univ-lille1.fr>
Cc: public-data-shapes-wg@w3.org, "Peter F. Patel-Schneider" <pfpschneider@gmail.com>
Message-ID: <20160315100232.GA31559@w3.org>
* Iovka Boneva <iovka.boneva@univ-lille1.fr> [2016-03-15 10:16+0100]
> Dear all,
> 
> You can look at my early working draft in which I tackle this problem.
> https://hal.archives-ouvertes.fr/hal-01288285

The link to the paper is in the upper right under the Files heading,
also here: <https://hal.archives-ouvertes.fr/hal-01288285/document>.


> I introduce a simple logical language that subsumes both ShEx and SHACL*.
> This allows me to propose a formal semantics for SHACL, including
> semantics for well founded recursion with stratified negation.
> The semantics is defined as a translation to the logical language.
> 
> I am currently working on describing the translation of ShEx to the
> logical language. I've got a reasonable clear idea of which part of
> ShEx is expressible in SHACL, but still need to work out the details
> of the syntactic restriction to be imposed.
> 
> On my opinion, this work not only allows to bring ShEx and SHACL
> closer, but also allows to better understand the expressiveness of
> both languages. The logical language is based on well-known
> formalisms such as logical programming, Datalog, Monadic Second
> Order logic, Presburger arithmetic, so should be easier to
> understand by a larger community.**
> 
> The current draft is incomplete regarding ShEx, but is complete
> regarding SHACL. I would be happy if somebody (Peter ?) familiar
> with SHACL and with formal methods could review it, and check
> whether my understanding of SHACL is correct, and whether my
> semantics captures correctly the intended semantics of SHACL
> 
> I apologise for the unfinished document, but preferred to
> communicate it early.
> 
> * Almost all ShEx and SHACL are captured, I left a few features
> apart to keep things simple.
> ** It turns out that the current ShEx semantics coincides with the
> new one introduced in this draft. The advantage of the new one is to
> be expressed using well known formalisms.
> 
> Best regards,
> Iovka
> 
> 
> Le 03/03/2016 18:15, Iovka Boneva a écrit :
> >Dear all,
> >
> >I am currently studying what restrictions should be made to ShEx
> >so that it can be compiled to SHACL. My hope is to manage to bring
> >the two languages closer, or even make them converge. Such
> >convergence however might require some changes to SHACL.
> >
> >The problem of repeated properties has been around for a while,
> >and my idea is to change the way we treat repeated properties in
> >ShEx and adopt something similar to qualified cardinalities in
> >SHACL.
> >
> >Another difference is the disjunction. Considering this concrete example:
> >
> >"A person has either a foaf:name, or a foaf:givenName and a
> >foaf:familyName"
> >
> >This is easily written in ShEx, but not in SHACL. I however think
> >that it would not require a big change to SHACL to be able to
> >easily handle such use cases.
> >
> >I hope to be able to make a concrete proposal of modified ShEx and
> >SHACL with the perspective of getting the two languages closer
> >(there are still some corner cases that I do not know how to deal
> >with). Hopefully it is possible to achieve this with modifications
> >of the two languages that are acceptable for the two communities.
> >
> >
> 
> 
> -- 
> Iovka Boneva
> Associate professor (MdC) Université de Lille
> http://www.cristal.univ-lille.fr/~boneva/
> +33 6 95 75 70 25
> 
> 

-- 
-ericP

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Received on Tuesday, 15 March 2016 10:02:39 UTC

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