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Re: ISSUE-100: Should ld-patch use a slash like sparql does, instead of as it currently does?

From: Sandro Hawke <sandro@w3.org>
Date: Mon, 18 Aug 2014 09:00:19 -0700
Message-ID: <53F22313.4070807@w3.org>
To: Alexandre Bertails <alexandre@bertails.org>, Linked Data Platform Working Group <public-ldp-wg@w3.org>
On 08/18/2014 08:17 AM, Alexandre Bertails wrote:
> Just to be more precise, this concerns the path expressions [1]. There
> are already slashes being used there.
>
> So I guess Sandro's proposal is to make LD path expressions *look
> like* SPARQL property paths.

That's not my proposal.

In general my view is that when the semantics are the same, the syntax 
should be the same, and when the semantics are different, the syntax 
should be different.  I hope we would all agree with that, in principle.

After that, it's details.   Important details, like whether the 
semantics are the same.

SPARQL as a path expression language and LD-Patch has path expression 
language.   There is no question they have different expressiveness.    
I would argue that when they are saying the same thing, however, they 
should use the same syntax.

For example, "start with node <a> then follow the <p1> property twice, 
then the <p2> property once".

In SPARQL that looks like:

<a> <p1>/<p1>/<p2>

in LD-Patch that looks like:

<a> /<p1>/<p1>/<p2>

The semantics are (arguably) the same; the syntax is extremely similar, 
differing only in the leading slash.

To me that difference is a show-stopper.  That's ISSUE-100.

       -- Sandro


> But unlike SPARQL, LD path expressions can be nested, and include
> constraints. SPARQL does that with FILTER and new constraints in the
> BGP. The grouping in SPARQL (using parenthesis) is very different from
> the constraints (square brackets and exclamation mark).
>
> I think it's a bad idea to make them feel like they behave the same,
> which could be induced by the choice of the syntax.
>
> I don't want to stop the group with syntactical questions thought, so
> just a -0.9 for me.
>
> Alexandre
>
> [1] https://dvcs.w3.org/hg/ldpwg/raw-file/ldpatch/ldpatch.html#path-expression
>
> On Mon, Aug 18, 2014 at 10:59 AM, Linked Data Platform  Working Group
> Issue Tracker <sysbot+tracker@w3.org> wrote:
>> ISSUE-100: Should ld-patch use a slash like sparql does, instead of as it currently does?
>>
>> http://www.w3.org/2012/ldp/track/issues/100
>>
>> Raised by:
>> On product:
>>
>>
>>
>>
>>
>
Received on Monday, 18 August 2014 16:00:29 UTC

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