Re: shapes-ISSUE-182 (Validation report): [Editorial] Clarifications need to section 3.0

On 9/29/16 8:57 PM, Holger Knublauch wrote:
> On 30/09/2016 1:40, RDF Data Shapes Working Group Issue Tracker wrote:
>> shapes-ISSUE-182 (Validation report): [Editorial] Clarifications need
>> to section 3.0
>> Raised by: Karen Coyle
>> On product:
>> Section 3.0 on validation talks about the validation results, but
>> doesn't explain clearly which properties are required and which are
>> optional. It also should refer to the shapes graph as the source of
>> the properties, not just to their appearance in the report. Some
>> examples:
>> " Value (sh:value)
>> Validation results may have a value for the property sh:value pointing
>> at a specific node that has caused the result."
>> - it isn't clear if sh:value MUST be returned if sh:value is coded in
>> the constraint, or if echoing back sThanh:value when it exists is itself
>> optional.
> I have added some prose into 3.4.3 to clarify how this property is
> populated. I hope this clarifies that sh:value is not coded in the
> constraint but is dynamically populated from the data graph.

Thanks, Holger. However, I'd change the wording from:

"Validation results may have a value for the property sh:value pointing 
at a specific node that has caused the result. "


"Validation results MAY include a property sh:value. The property takes 
as its object the specific node in the data graph that caused the 
result. This object can be any RDF term (IRI, literal, or blank node)."

Then I'd leave off the "for example" part, but it doesn't hurt anything.

"pointing to" has the same problem as the "linking to" comment that 
Peter first brought up. For this reason it may be best to use the 
terminology of triples when speaking of relationships between the 
components of triples, which are only defined positionally, not as links 
or pointers.

I assume that an sh:value with a blank node as object may not always be 
informative, but it is a possibility.

>> Declaring the Severity of a Constraint uses "can" not "MAY",
>> and gives the default as sh:Violation (Does that mean T/F cannot have
>> a default?). Better wording would be:
>> "The severity level of a constraint violation MAY be coded in the
>> constraint of a shapes graph using the property sh:severity, which
>> takes as its value one of the SHACL pre-defined severities, or a
>> locally defined severity." (followed by remaining sentences)
> I have applied similar wording to 3.4.8.

I don't see changes in those sections - did the changes actually go in?

>> Also, the example given shows the shapes graph, but would be more
>> informative if it also included the validation report that results.
> For this to happen, I would also need to create a data graph, then the
> results graph. This would easily fill two pages. While I agree this
> would be "informative", I am honestly not convinced whether this is
> worth the effort. With every paragraph that we add, more stuff will need
> to be reviewed (and no doubt someone will not like something about
> them). The current example includes # comments that are IMHO clear
> enough about what will happen. But if you feel strongly about this, I
> can add expand on the example.

I do think that such an example would be good. It may be possible to 
show snippets rather than whole SHACL documents. Another option is to 
put examples at the end of the section. (The turtle syntax document does 

>> Note that examples throughout do not include sh:severity or sh:message
>> in constraints, which requires some explanation, perhaps in the
>> introductory area where examples are described. (I presume that it is
>> expected that most or many constraints will include a severity, so it
>> would be a normally occurring property, and that sh:message will also
>> be common.)
> I have added two sentences enumerating the mandatory properties:
>                     The properties <code>sh:focusNode</code> and
> <code>sh:severity</code> are the only mandatory properties of all
> validation results.
>                     The property
> <code>sh:sourceConstraintComponent</code> is mandatory for validation
> results produced by violations of <a>constraint components</a>.
> I hope this addresses the role of mandatory vs optional properties?

Yes, I believe it does. Thanks.

>> The Example validation report in section 2.2 (Filter shapes) has
>> sh:severity and sh:message although those are not shown in the shapes
>> graph.
> sh:severity is optional and therefore not shown (the default is
> sh:Violation).
> sh:message is automatically produced by the engine, although I have
> recently opened a ticket to also allow it at individual constraints.
> So technically that's all OK. I could add an explanation about where
> these properties are coming from, but that's kinda repetitive and would
> require forward-references to later sections.

You could comment in the example with something like "# See Violations 
section" - that way, people know that it's something that will be 
explained later, but it doesn't take up much space.

> As always, it is possible to have different opinions about such
> editorial changes. If you can live with the current state, let me know
> so we can close this ticket. Otherwise, please respond with what else
> needs to be changed.

I discovered where it is said (although not quite directly) that a 
validation report is only created when the focus node is NOT valid, i.e. 
fails to meet the criteria of the constraints: it's in the terminology 
section in the box that begins "Data Graph, Shapes Graph...". It says there:

" A node in a data graph is said to validate against a shape if 
validation of that node against the shape neither produces any 
validation results nor results in a failure."

That's a bit subtle, and if nothing else it also needs to be said in the 
actual validation section. But I think it should be clearer and it say 
that a validation report is only produced for focus nodes that *fail* to 
validate against the constraints. It needs to be very clear that the 
validation report is not a report of all of the results of the 
validation process, but only a report on the failures. Its name does not 
imply that; actually, it implies that it is reporting on the results of 
the act of validation, which has at least two possible outcomes: 
pass/fail (or T/F). So it is important to make this point.


p.s. Note that I am always willing to actually make the changes myself 
in my fork if that is easier than doing this through email.

> Thanks,
> Holger

Karen Coyle
m: 1-510-435-8234
skype: kcoylenet/+1-510-984-3600

Received on Saturday, 1 October 2016 01:23:40 UTC