Re: eliminating property constraints

Thanks, Peter. I'll try to get all of these done today, before 
tomorrow's meeting.

kc

On 11/22/16 8:43 AM, Peter F. Patel-Schneider wrote:
> I'm not sure what scope you want this conversation to have.  In November I
> have initiated six threads in the public comments mailing list.  I
> previously initiated quite a few more.
>
> I'll limit this message to the November threads.  I do note that most of my
> previous messages are about what substantive problems in the SHACL document.
> I don't view any of these messages as simply editorial although some of them
> may have been addressed by other changes to SHACL.
>
>
> Thread: some comments on SHACL editors' draft of 8 November (Friday, 11
> November)
>
> This thread is about the continuing problems in the SHACL document with
> inadequate description of the basic terminology and operation of SHACL.  In
> the message I not only stated the basic problem but also put forward several
> examples of it.  There have been changes made to the SHACL document to
> address some of the examples, and one of them has been associated with
> ISSUE-192.  However, I don't see that anything has been done to address the
> continuing serious problem that I have brought up again.  This problem was
> the subject of ISSUE-142, which was closed by the working group.  I
> expressed my disappointment that an important issue was closed without being
> satisfactorily addressed.  It is even not just that the document is unclear
> about terminology and processing but that the document says things that are
> counter to my understanding of what SHACL is supposed to be or be doing.
> So, no, there is not a complete list of open working group issues related to
> my substantive comments.
>
> Thread: on removing pre-binding from the core of SHACL (Saturday, 12
> November)
>
> There is no issue linked to this email thread in
> https://www.w3.org/2014/data-shapes/wiki/Comments/September2016/
> However, ISSUE-202 was created for it.   I do note that it is not in the
> charter of the SPARQL Maintenance (EXISTS) Community Group to provide a
> definition of pre-binding.
>
> Thread: two interesting test cases for SHACL (Monday, 14 November)
>
> This email message presented two separate test cases for SHACL to illustrate
> two current problems in the description of SHACL.
>
> The first has to do with what happens when a node in a shapes graph is both
> a shape and a property constraint.  I had brought up this point before, but
> decided to present a test case for it.  I don't see a working group issue
> for the problem.
>
> The second test case has to do with the fundamental notion of what makes a
> shape in SHACL.  At the time then I wrote this message a shape in SHACL was
> a node in a shapes graph with SHACL type sh:Shape or expected type sh:Shape.
> Subsequently this has been changed so that more nodes are shapes, including
> those nodes that are subjects of target properties.  There is ISSUE-209 on a
> related topic, but that topic has aleady been the subject of a long email
> thread starting at
> https://lists.w3.org/Archives/Public/public-rdf-shapes/2016Oct/0029.html
>
> The changes to the SHACL document made in response to the this second test
> case have made a significant change to SHACL.  This significant change was
> made without any issue being raised and is inadequately described in the
> change section of the document.
>
> There should be two new issues on these topics as well as a discussion in
> the working group about how the process for making significant changes to
> SHACL has broken down.
>
> Thread: eliminating property constraints (Saturday, 19 November)
>
> ISSUE-211 has been created for this thread.
>
> Thread: on ISSUE-196 (Tuesday, 22 November)
>
> This is a new email thread having to do with problems in the closing of
> ISSUE-196.
>
> Thread: undocumented changes to SHACL (Tuesday, 22 November)
>
> This is a new email thread having to do with inadequate description of
> substantive changes to SHACL.  It may also be that these substantive changes
> have not had any working group discussion.
>
> Peter F. Patel-Schneider
> Nuance Communications
>
>
> On 11/20/2016 01:29 PM, Karen Coyle wrote:
>> Peter, I have edited the page of received comments [1] and have created issues
>> for as many of the items that I could. I would love to say that it is all
>> complete and correct, but am not so confident. If you have time to review the
>> list and the newly raised items on tracker,[2]  I would appreciate it.
>>
>> kc
>> [1] https://www.w3.org/2014/data-shapes/wiki/Comments/September2016/
>> [2] https://www.w3.org/2014/data-shapes/track/issues/raised
>>
>> p.s. for Arnaud - the missing issue #206 is because I had created a duplicate,
>> which I then deleted
>>
>> On 11/19/16 6:08 AM, Peter F. Patel-Schneider wrote:
>>> SHACL currently has shapes, constraints, constraint components, parameters,
>>> and the special property sh:property.  This leads to a complex formalism
>>> that the SHACL document continues to struggle to adequately describe.
>>>
>>> This complexity is not necessary.  Both shapes and constraints can be merged
>>> into a single notion of shapes.  The special property sh:property can be
>>> turned into the single parameter of a new constraint component.
>>>
>>> Under this new setup for SHACL shapes are uniformly validated in a context
>>> where there are focus nodes and value nodes.  Shape validation from targets
>>> is done in a context for each target node with the focus node being the
>>> target node and the set of value nodes being the singleton containing only
>>> the target node.  Constraint components in a shape are each validated in the
>>> context of the shape.
>>>
>>> The new constraint component, with parameter sh:property, works by
>>> validating its shape argument in a new context for each value node of the
>>> current context.  This new context has as its focus node the original value
>>> node and has as its value nodes the set of value nodes for the sh:property
>>> or sh:path in the shape, just as before.
>>>
>>> This change is largely just a change in the description of SHACL.  There
>>> are, however, a few minor changes to SHACL itself.  First, there would be a
>>> new constraint component with sh:property as its sole parameter.  Second,
>>> the argument for this parameter would be a shape, albeit one that has to
>>> have a value for either sh:predicate or sh:path.  It would be possible make
>>> the expected type for sh:property values be a subclass of sh:shape, but
>>> users of SHACL would not need to know that this was the case and the only
>>> reason to do so would be to support the validation of SHACL shapes graphs in
>>> SHACL.
>>>
>>> This change to SHACL would help greatly in decreasing the complexity of the
>>> langauge and permit a better and more streamlined description of SHACL.
>>>
>>>
>>> Peter F. Patel-Schneider
>>> Nuance Communications
>>>
>>>
>>
>

-- 
Karen Coyle
kcoyle@kcoyle.net http://kcoyle.net
m: 1-510-435-8234
skype: kcoylenet/+1-510-984-3600

Received on Tuesday, 22 November 2016 16:54:16 UTC