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Re: Node vs focus node (Was: Re: shapes-ISSUE-181: SHACL conformance for partial validation reports [SHACL Spec])

From: Karen Coyle <kcoyle@kcoyle.net>
Date: Tue, 4 Oct 2016 08:03:27 -0700
To: public-data-shapes-wg@w3.org
Message-ID: <1b556d10-2bbc-b75c-965d-9ee95c454210@kcoyle.net>
Here's what I see as the offending sentence, which is also one that 
Peter cited:

"The focus nodes may also be determined as
part of the validation of constraints that include references to shapes
using properties such as sh:shape and sh:or."

That is in the first paragraph of 2.0.

See:

(2.1) "Targets are ignored when a shape is processed as a nested shape 
in shape-based constraint components (i.e. sh:shape), logical constraint 
components (i.e. sh:or), filter shapes (sh:filterShape) or, for SHACL 
Full, in the evaluation of the sh:hasShape SPARQL function as defined in 
appendix A."

I'm not sure what "targets are ignored" actually means, unless it means 
that the entire data graph is the target. If you ignore a target, then 
what are you paying attention to? Or is the meaning that sh:shape and 
sh:or extend the target? Where you do first connect with the data graph 
if there is no target?

kc

On 10/3/16 8:16 AM, Karen Coyle wrote:
> I still find the definition of focus node circular. The focus node is
> defined as (in terminology):
>
> "A node in the data graph that is validated against a shape is called a
> focus node."
>
> This essentially says: if it is validated against a shape, then it is a
> focus node.
>
> But there is a focus node constraint that defines constraints on the
> focus node. So now there is a constraint defined on a focus node that
> (as per the terminology) cannot exist until validation takes place.
>
> Also note that in the validation section, the only mention of focus
> nodes is in the validation report. There is no description of using (or
> creating) focus nodes in validation. Since the Targets section does not
> define focus nodes, only targets, they have not been defined anywhere in
> sections 2 or 3.
>
> kc
>
> On 10/2/16 11:35 AM, Dimitris Kontokostas wrote:
>> Hi Karen,
>>
>> On Sun, Oct 2, 2016 at 6:54 PM, Karen Coyle <kcoyle@kcoyle.net
>> <mailto:kcoyle@kcoyle.net>> wrote:
>>
>>
>>     Dimitris, the part of the spec we are talking about is the
>>     validation section. If Filters take place as part of validation,
>>     then we should move them to the validation section. If validation
>>     takes place after the filters are applied, then at that point it is
>>     a focus node. My understanding (and I would like to hear from
>>     others) is that the entire process of validation takes place on
>>     focus nodes.
>>
>>
>> Section 2 describes shapes, targets, filters and constraints, then
>> section 3 describes validation as well as the data graph, shapes graph
>> and validation results.
>> All constructs described in section 2 are referenced in the validation
>> definition but any feedback to restructure these sections is more than
>> welcome.
>>
>> Based on my understanding,
>> filters are of course part of the validation process but the term focus
>> node is used when the nodes reach the constraints of the shape.
>> As I said, I do not have a strong opinion on this and would be happy to
>> discuss this further during the next call or hear what others have to say
>>
>>     I'm also a bit concerned about that "iff" - while it is a commonly
>>     known shorthand for "if and only if" it is not English language and
>>     not universally known, so I think that "iff" should be written as
>>     "if and only if" when used in a sentence. If the section were in an
>>     abstract syntax then I think that "iff" would be appropriate. This
>>     section is not that formal. I do find it used in W3C documents when
>>     describing formal rules (see section 2.1 of the SWRL document [1]).
>>
>>
>> I replaced iff according to your suggestion.
>>
>> Thanks,
>> Dimitris
>>
>> --
>> Dimitris Kontokostas
>> Department of Computer Science, University of Leipzig & DBpedia
>> Association
>> Projects: http://dbpedia.org, http://rdfunit.aksw.org,
>> http://aligned-project.eu
>> Homepage: http://aksw.org/DimitrisKontokostas
>> <http://aksw.org/DimitrisKontokostas>
>> Research Group: AKSW/KILT http://aksw.org/Groups/KILT
>> <http://aksw.org/Groups/KILT>
>>
>

-- 
Karen Coyle
kcoyle@kcoyle.net http://kcoyle.net
m: 1-510-435-8234
skype: kcoylenet/+1-510-984-3600
Received on Tuesday, 4 October 2016 15:04:06 UTC

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