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

On Mon, Aug 18, 2014 at 3:38 PM, Andy Seaborne <andy@apache.org> wrote:
> On 18/08/14 17:55, Sandro Hawke wrote:
>>
>> On 08/18/2014 09:30 AM, Alexandre Bertails wrote:
>>>
>>> On Mon, Aug 18, 2014 at 12:00 PM, Sandro Hawke <sandro@w3.org> wrote:
>>>>
>>>> On 08/18/2014 08:17 AM, Alexandre Bertails wrote:
>
>
>>> The intuition is that when you see `node(s) / p1 / p2`, it means that
>>> you start with the current nodes and try to follow p1, this gives you
>>> a new set of nodes, on which you can now apply p2.
>>
>>
>> Same with SPP.
>
>
> Absolutely.
>
> { ?x :p1/:p2 ?y }
>
> ?x can be a collection of nodes.
>
> Do you have a concrete example of where there are differences?

I think there is some misunderstanding.

In `Bind ?foo ?x /:p1/:p2 .`, ?x is replaced by its previously bound
value. It is never left unknown and start with a concrete value. The
operation carries a set of nodes, the final value being here bound to
?foo. No need for a solution mapping.

>
> The charter has a "Liaison" which includes SPARQL WG (tricky as it formally
> does not exist) - why not start by sending a message the SPARQL comments
> list?

I am not sure what we would ask to the SPARQL WG. The LD Patch
semantics don't share much with SPARQL.

Alexandre

>
>         Andy
>
>
>>> Then you may object that this seems to not work anymore when used in
>>> constraints eg. `node(s) / p1 / p2 [ / p3 ]`. Actually, the set of
>>> nodes when in a constraint is there *implicitly*, a constraint being
>>> exactly like a higher-order function, whose argument is the set of
>>> nodes before getting into the constraint.
>>
>>
>> I'm not concerned with constraints for the purposes of issue-100.
>>
>>> / is used consistently in the whole path, including its semantics.
>>
>>
>> I'm not saying it's internally inconsistent, just that it's gratuitously
>> different from SPP, as far as I can tell.
>>
>> I think it's very important that we borrow whichever bits of SPP work
>> reasonably well for LD-Patch.
>>
>>> Now again, same argument as last email, changing that would be a -0.9
>>> for me.
>>>
>>>> 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.
>>>
>>> A show-stopper? As in -1 or -0.9 ?
>>
>>
>> I'm not going to -1 any design decisions here, but I think it's critical
>> to answer the questions I raise above.  I'm entirely confident we'll
>> have to answer them later with this design, and at that point it'll be
>> much harder.
>>
>>         - s
>>
>>> Alexandre
>>>
>>>>        -- 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 19:50:10 UTC