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Re: RDF-ISSUE-95 (turtle-inverse): Turtle Inverse Property Syntax [RDF Turtle]

From: Richard Cyganiak <richard@cyganiak.de>
Date: Wed, 22 Aug 2012 21:59:18 +0100
Message-Id: <237A4372-2687-4738-BC49-64BCCB64004F@cyganiak.de>
To: RDF Working Group <public-rdf-wg@w3.org>
I support the "do nothing" position.

Rationale:

1. From a spec development point of view, Turtle is best understood as the "SPARQL data language". If this is added to Turtle, it should be added to SPARQL too.

2. It's a feature that I'd love to use, but it's not worth holding up SPARQL 1.1 for it.

3. Some future WG can add this feature. It will be harder in the future than it is now, but such is life. (I hope that in the future, updating Turtle (and TriG) will be the job of SPARQL WG.)

Best,
Richard


On 22 Aug 2012, at 16:12, RDF Working Group Issue Tracker wrote:

> RDF-ISSUE-95 (turtle-inverse): Turtle Inverse Property Syntax [RDF Turtle]
> 
> http://www.w3.org/2011/rdf-wg/track/issues/95
> 
> Raised by: Gavin Carothers
> On product: RDF Turtle
> 
> Use cases
> =========
> 
> Reduce otherwise verbose reuse of an object for many subjects.
> (From TimBL http://lists.w3.org/Archives/Public/public-rdf-comments/2012Jul/0007.html)
> 
> Examples:
> 
>    foaf:Person is a of :Alice, :Bob, :Charlie, :David, :Elisa .
> 
> vs.
> 
>    :Alice a foaf:Person .
>    :Bob a foaf:Person .
>    :Charlie a foaf:Person .
>    :David a foaf:Person .
>    :Elisa a foaf:Person .
> 
> Allowing a predicate to be used in either direction
> (From TimBL http://lists.w3.org/Archives/Public/public-rdf-comments/2012Jul/0007.html)
> 
>    :Alice  foaf:age 38;
>        g:child :Bob, :Charlie;
>        is  g:child of  :Edna, :Fred;
>        foaf:basedNear :London;
>        is dc:author of [ dc:title "My life"; dc:date "1999"] .
> 
> 
> Compatibility with N3 has not been considered as a use case.
> 
> Rationale
> =========
> 
> Decreases the motivation for the anti-pattern to define both property
> and inverse of the property for all properties. In other words, if you
> can write  "is child of" you don't need to define a separate "parent"
> property.
> 
> No emerging consensuses on the need to reduce otherwise verbose reuse
> of an object for many subjects.
> 
> 
> Objections
> ==========
> 
> English-centric "is ... of" is English-centric.
> 
> Moves Turtle away from stated goal of compatibility with SPARQL 1.1.
> 
> 
> Revised ^ Syntax
> ================
> 
>    foaf:Person ^a :Alice, :Bob, :Charlie, :David, :Elisa .
> 
>    :Alice  foaf:age 38;
>        g:child :Bob, :Charlie;
>        ^g:child :Edna, :Fred;
>        foaf:basedNear :London;
>        is dc:author of [ dc:title "My life"; dc:date "1999"] .
> 
> Objections to Revised Syntax
> ============================
> 
> Not compatible with N3
> 
> Not compatible with SPARQL Update or SPARQL CONSTRUCT
> 
> No implementation experience
> 
> 
> Objections to both original syntax and revised syntax
> =====================================================
> 
> Turtle is a reasonably settled languages, changes made by the working
> group so far have been limited to areas of existing differences in
> implementation.
> 
> No demand over years of implementation experience
> 
> Harder to teach Turtle
> 
> No implementation experience in SERIALIZING to these inverse forms.
> 
> 
> Proposals
> =========
> 
> 1. Add is .. of syntax to Turtle.
> 
>    1.1. Allowing "literals" in any subject position by syntax,
> however the RDF model disallows literal as subject. (somewhat as
> SPARQL but SPARQL does not support is ... of syntax)
> 
>    1.2. Attempting to limit use of "literals" in subject position to
> only is ... of predicates in grammar (Not as SPARQL)
> 
> 
> 2. Add ^ property path syntax to Turtle.
> 
>    1.1. Allowing "literals" in any subject position by syntax,
> however the RDF model disallows literal as subject. (As SPARQL in
> query blocks, however SPARQL disallows path syntax in triple assertion
> syntax)
> 
>    1.2. Attempting to limit use of "literals" in subject position to
> only ^ predicates in grammar (Not as SPARQL and SPARQL disallows path
> syntax in triple assertion syntax.)
> 
> 
> 3. Add both ^ property path syntax and "is ... of" syntax.
> 
>    1.1. Allowing "literals" in any subject position by syntax,
> however the RDF model disallows literal as subject. (As SPARQL in
> query blocks, however SPARQL disallows path syntax in triple assertion
> syntax)
> 
>    1.2. Attempting to limit use of "literals" in subject position to
> only ^ predicates and is .. of predicates in grammar (Not as SPARQL
> and SPARQL disallows path syntax in triple assertion syntax and SPARQL
> does not support is ... of)
> 
> 4. Do nothing.
> 
> 
> 
Received on Wednesday, 22 August 2012 20:59:47 UTC

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