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Joseph, You might want to look at my blog post on RDF classes:

http://kcoyle.blogspot.com/2014/11/classes-in-rdf.html

and the article by Baker-Coyle-Petiya

http://kcoyle.net/LHTv32n4preprint.pdf

There are actually no "constraints" in RDF, just potential inferences. 
The inferences are based on the stated domains and ranges of the 
properties. There are examples of this in the Baker et al article using 
RDA, FRBRer and BIBFRAME. There is no conflict with a subject being 
inferred as being an instance of more than one class as long as the 
classes themselves are not declared as disjoint. (The article explains 
this better than I can in an email. ) The documentation for RDA, 
BIBFRAME and FRBRer all presents classes as determinants of data 
structure. This, to me, is a common error in RDF development. That any 
subject can be an instance of more than one class is necessary for the 
RDF graph's flexibility, and should be proof that classes do not 
constraint your data to a single graph structure.

The declared domains of properties only come into play if inferencing is 
applied. A big question, therefore, is whether any inferencing will be 
done at all over the data. The utility of, for example, the RDA classes 
to me is that it allows you to do simple queries for categories of 
triples, e.g. "give me all of the work triples for the manifestation 
with this ISBN." Other than that you can ignore the fact that domains 
have been declared if they don't serve your needs.

Your question, however, brings up a much larger question that I haven't 
seen discussed anywhere, which is: what kinds of operations do we expect 
to perform over library data in RDF? That question really should be 
answered before domains and ranges are defined, because that is the 
function of those capabilities of RDF.

kc











On 1/5/15 12:52 PM, Joseph Kiegel wrote:
> A comparison of BIBFRAME and RDA in RDF (referred to below as RDA), in 
> an attempt to map RDA to BIBFRAME, raised the issue of constrained vs 
> unconstrained schemas.
>
> The full set of RDA properties is constrained by the RDA classes of 
> Agent, Work, Expression, Manifestation and Item.  That is, each 
> property is related to a specific class when appropriate:  e.g. 
> abridgementOfExpression and abridgementOfWork.  A parallel set of 
> properties has been created where the constraints of class are 
> lifted:  e.g. abridgementOf.  This unconstrained version of RDA loses 
> the context of some properties but is intended to facilitate mapping 
> to schemas that do not use the FRBR model underlying RDA.
>
> BIBFRAME is a constrained schema, but constrained by different 
> classes: Agent, Work, and Instance.  There is no unconstrained version 
> of BIBFRAME.
>
> A mapping of RDA to BIBFRAME presents choices and challenges.
>
> Is it better to use constrained RDA, which causes explicit conflicts 
> of domain:  e.g. mapping rdam:reproductionOfManifestation to 
> bf:reproduction and rdai:reproductionOfItem to bf:reproduction?
>
> Or is it better to use unconstrained RDA, which still has conflicts 
> (an unconstrained domain vs a constrained one in BIBFRAME):  e.g. 
> mapping rdau:reproductionOf to bf:reproduction?
>
> It is not obvious which is the better choice.  Although perhaps we 
> need both mappings, each with its own problems regarding original and 
> destination domains.
>
> A corollary of the question is that any roundtrip RDA -> BF -> RDA is 
> lossy. If constrained RDA is used as a starting point, RDA classes are 
> lost in the mapping itself, and if unconstrained RDA is used, classes 
> are lost prior to mapping. Either way, RDA classes cannot be recovered 
> in a BF -> constrained RDA mapping.
>

-- 
Karen Coyle
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