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Re: ISSUE-140: Suggestion to close

From: Karen Coyle <kcoyle@kcoyle.net>
Date: Mon, 31 Oct 2016 18:53:57 -0700
To: public-data-shapes-wg@w3.org
Message-ID: <dfa43932-9b97-0ee0-2c5a-8c249f9d77e9@kcoyle.net>


On 10/31/16 6:30 PM, Holger Knublauch wrote:
>
>
> On 1/11/2016 11:16, Karen Coyle wrote:
>>
>>
>> On 10/31/16 4:29 PM, Holger Knublauch wrote:
>>>
>>>
>>> On 1/11/2016 1:10, Karen Coyle wrote:
>>>>
>>>>
>>>> On 10/31/16 6:46 AM, Dimitris Kontokostas wrote:
>>>>> I also feel that the core of Eric's issue is solved but if we go with
>>>>> this PR as is, we move from one edge to another.
>>>>> However, I also agree that targetNode can be an antipattern that we do
>>>>> not want to promote so much with the spec
>>>>> (binding shapes with specific nodes in advance)
>>>>>
>>>>> Maybe we could try a mix of different target schemes as well as some
>>>>> examples without targets.
>>>>> But we should somehow differentiate the target-based validation
>>>>> with the
>>>>> targetless/ShEx validation.
>>>>
>>>> I, too, think that we should have some examples without targets, but
>>>> for a different reason: I have use cases where a simple constraint on
>>>> a property is going to be not only sufficient but the only
>>>> possibility, either because the data does not specify classes, or
>>>> because I cannot know what classes it uses. It would make sense,
>>>> though, to actually address this in the document rather than slip it
>>>> into examples without an explanation.
>>>
>>> In those cases we could use sh:targetObjectsOf and/or
>>> sh:targetSubjectsOf. We don't have many examples on these properties
>>> anyway.
>>>
>>> Holger
>>
>> Are you saying that the examples as edited by Eric that do not have
>> targets are invalid SHACL?
>
> No, I never said this.
>
> Holger

So then I guess I don't see the problem. - kc

>
>
>> If so, then could you give an example of a valid shape with zero targets?
>>
>> To be more specific, this is the example for 4.2.2:
>>
>> ex:DatatypeExampleShape
>>     a sh:Shape ;
>>     sh:property [
>>         sh:predicate ex:age ;
>>         sh:datatype xsd:integer ;
>>     ] .
>>
>> from Eric's version at:
>> https://ericprud.github.io/data-shapes/shacl/
>>
>> kc
>>
>>>
>>>
>>>>
>>>> It does make sense to me that section 4 show examples without targets,
>>>> and that could be addressed in the intro to that section by saying
>>>> that targets and filters are optional, and that the constraints in the
>>>> section work equally well with shapes that contain targets and
>>>> filters. This section is about the constraints, and adding targets to
>>>> the examples, IMO, complicates the examples and makes them less clear.
>>>> (BTW, shapes without targets and filters make more sense than shapes
>>>> without constraints, and there are shapes without constraints in the
>>>> section on targets which are implied to be complete - I don't think
>>>> they are.)
>>>>
>>>> Note that the definition of shapes is: "A shape provides a set of zero
>>>> or more targets, filters, constraints and parameters of constraint
>>>> components that specify how a set of nodes from the data graph are
>>>> validated against the shape." Although it says "zero or more" there
>>>> were previously no examples with "zero" targets and filters.
>>>>
>>>> kc
>>>>
>>>>>
>>>>> On Mon, Oct 31, 2016 at 2:41 AM, Holger Knublauch
>>>>> <holger@topquadrant.com <mailto:holger@topquadrant.com>> wrote:
>>>>>
>>>>>
>>>>>
>>>>>     On 31/10/2016 17:54, Eric Prud'hommeaux wrote:
>>>>>
>>>>>         * Holger Knublauch <holger@topquadrant.com
>>>>>         <mailto:holger@topquadrant.com>> [2016-10-31 09:29+1000]
>>>>>
>>>>>             Thanks for your work on the results tables, Eric. I have
>>>>>             seen your pull
>>>>>             request but I disagree with deleting the sh:targetXY
>>>>> triples
>>>>>             from the
>>>>>             examples. These need to be restored IMHO.
>>>>>
>>>>>         I think this gets to the heart of the issue. In earlier
>>>>> discussions,
>>>>>         several of us said that dedicating a schema to a specific
>>>>> dataset is
>>>>>         an antipattern. targetNode is particularly problematic in tha
>>>>>         respect
>>>>>         but even the rest of target* leave open questions. Most of
>>>>> your
>>>>>         examples use targetClass which requires a specific type arc.
>>>>> If the
>>>>>         data serves multiple purposes (e.g. an ex:SalesContact and an
>>>>>         ex:User), you need discriminating type arcs for all the roles
>>>>> it may
>>>>>         play.
>>>>>
>>>>>
>>>>>     ISSUE-140 originally was about clarifying that *in addition to
>>>>>     graph-based validation using targets* SHACL engines should support
>>>>>     an interface to validate individual nodes by other means. Targets
>>>>>     are part of SHACL. By leaving them out of the examples you may get
>>>>>     closer to your (controversial) viewpoint, but it doesn't help to
>>>>>     explain SHACL's graph-based mode of operation. The boxes are
>>>>> labeled
>>>>>     "shapes graph" and "data graph", so it's fair to assume that these
>>>>>     are meant to be consistently used as explained. We have various
>>>>>     sections that explain how the targets are used. It's valuable to
>>>>>     have consistency, and examples of targets have been requested
>>>>>     multiple times.
>>>>>
>>>>>
>>>>>         Is TopQuadrant's use case addressed by the target* section
>>>>> as it
>>>>>         stands in my proposal?
>>>>>
>>>>>
>>>>>     I don't think your branch has made changes to the target sections
>>>>>     from the main branch? But yes, the current design addresses the
>>>>> use
>>>>>     cases that we have for SHACL.
>>>>>
>>>>>     Holger
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>             (See https://github.com/w3c/data-shapes/pull/22/files
>>>>> <https://github.com/w3c/data-shapes/pull/22/files>)
>>>>>
>>>>>             Holger
>>>>>
>>>>>
>>>>>             On 26/10/2016 22:01, Eric Prud'hommeaux wrote:
>>>>>
>>>>>                 * Holger Knublauch <holger@topquadrant.com
>>>>>                 <mailto:holger@topquadrant.com>> [2016-10-07
>>>>> 10:59+1000]
>>>>>
>>>>>                     We are down to 14 open issues right now, and I am
>>>>>                     keen on making further
>>>>>                     progress. My take is the sooner we have the formal
>>>>>                     list of open issues down,
>>>>>                     the earlier we can focus on the informal issues
>>>>>                     raised from the outside.
>>>>>
>>>>>                     ISSUE-140 was last discussed
>>>>>
>>>>> https://www.w3.org/2016/09/27-shapes-minutes.html#item08
>>>>> <https://www.w3.org/2016/09/27-shapes-minutes.html#item08>
>>>>>
>>>>>                     but I have to confess I did not quite understand
>>>>>                     what problem Eric was
>>>>>                     referring to. It seems that Eric was merely
>>>>> pointing
>>>>>                     out that validation can
>>>>>                     be defined independently from specific node
>>>>>                     selection (i.e. target)
>>>>>                     mechanisms. I of course agree with that. Could you
>>>>>                     clarify?
>>>>>
>>>>>                 I've forked the spec and gone through about half of
>>>>> the
>>>>>                 examples (up
>>>>>                 to sh:and) and added tabular summaries:
>>>>>
>>>>> https://ericprud.github.io/data-shapes/shacl/
>>>>> <https://ericprud.github.io/data-shapes/shacl/>
>>>>>
>>>>>                 I believe this helps readers and addresses this issue.
>>>>>
>>>>>
>>>>>                     Ted seemed to request some more detail in the spec
>>>>>                     about how the validation
>>>>>                     of individual nodes is supposed to happen. We
>>>>>                     already have one such
>>>>>                     interface, the sh:hasShape function, which can be
>>>>>                     invoked to trigger the
>>>>>                     validation of a given node against a given
>>>>> shape. We
>>>>>                     have no such interface
>>>>>                     for the case in which only a node is given. But we
>>>>>                     also don't formally
>>>>>                     define how the validation is triggered in the
>>>>>                     general, whole-graph case. We
>>>>>                     could potentially add a function
>>>>>                     sh:validateNode(?node) that validates the
>>>>>                     given node against all shapes with matching
>>>>> targets.
>>>>>                     But then people will
>>>>>                     likely complain that we are adding yet another
>>>>>                     SPARQL implementation
>>>>>                     requirement. Alternatively, Ted, could you clarify
>>>>>                     how else we can meet your
>>>>>                     requirement?
>>>>>
>>>>>                     Thanks,
>>>>>                     Holger
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>                     On 23/09/2016 10:11, Holger Knublauch wrote:
>>>>>
>>>>>                         I had raised
>>>>> https://www.w3.org/2014/data-shapes/track/issues/140
>>>>> <https://www.w3.org/2014/data-shapes/track/issues/140>
>>>>>                         myself,
>>>>>                         primarily as a reminder that validation of
>>>>>                         individual nodes should be
>>>>>                         mentioned in the spec. I have meanwhile
>>>>> added a
>>>>>                         sentence which IMHO
>>>>>                         addresses this need.
>>>>>
>>>>>                         PROPOSAL: Close ISSUE-140 as addressed by
>>>>> https://github.com/w3c/data-shapes/commit/2046305962be7cd47400e7a2b51cd2841dca398c
>>>>>
>>>>>
>>>>> <https://github.com/w3c/data-shapes/commit/2046305962be7cd47400e7a2b51cd2841dca398c>
>>>>>
>>>>>
>>>>>
>>>>>                         Holger
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>> --
>>>>> 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
>>>>> Research Group: AKSW/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, 1 November 2016 01:54:33 UTC

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