On 9/16/13 6:29 AM, [log in to unmask] wrote:
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> I'd suggest that perhaps the confusion arises because "This instance is (not) 'valid' according to that ontology." might be inferred from an instance and an ontology (under certain conditions), and that's the soul of what we're asking when we define constraints on the data. Perhaps OWL can be used to express conditions of validity, as long as we represent the quality "valid" for use in inferences.

Based on the results of the RDF Validation workshop [1], validation is 
being expressed today as SPARQL rules. If you express the rules in OWL 
then unfortunately you affect downstream re-use of your ontology, and 
that can create a mess for inferencing and can add a burden onto any 
reasoners, which are supposed to apply the OWL declarations.

One participant at the workshop demonstrated a system that used the OWL 
"constraints" as constraints, but only in a closed system. I think that 
the use of SPARQL is superior because it does not affect the semantics 
of the classes and properties, only the instance data, and that means 
that the same properties can be validated differently for different 
applications or under different contexts. As an example, one community 
may wish to say that their metadata can have one and only one dc:title, 
while others may allow more than one. You do not want to constrain 
dc:title throughout the Web, only your own use of it. (Tom Baker and I 
presented a solution to this on the second day as Application Profiles 
[2], as defined by the DC community).

kc
[1] https://www.w3.org/2012/12/rdf-val/agenda
[2] 
http://www.w3.org/2001/sw/wiki/images/e/ef/Baker-dc-abstract-model-revised.pdf


> - ---
> A. Soroka
> The University of Virginia Library
>
> On Sep 13, 2013, at 11:00 PM, CODE4LIB automatic digest system wrote:
>
>> Also, remember that OWL does NOT constrain your data, it constrains only the inferences that you can make about your data. OWL operates at the ontology level, not the data level. (The OWL 2 documentation makes this more clear, in my reading of it. I agree that the example you cite sure looks like a constraint on the data... it's very confusing.)
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-- 
Karen Coyle
[log in to unmask] http://kcoyle.net
m: 1-510-435-8234
skype: kcoylenet