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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 09:09:41 -0700
Message-ID: <53F22545.9090300@w3.org>
To: Alexandre Bertails <alexandre@bertails.org>, Linked Data Platform Working Group <public-ldp-wg@w3.org>
On 08/18/2014 09:00 AM, Sandro Hawke wrote:
> 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.
                ^ has
> 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 16:09:49 UTC

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