ons 2008-03-26 klockan 06:31 -0700 skrev Karen Coyle:
>
> So what our discussion here started as was trying to figure out how the
> properties can be defined such that we can create an RDA AP that
> reflects the current stated data described in RDA, and yet be able to
> move beyond that into more rigorous data without sacrificing
> interoperability. I think that Mikhail answered that with "non-literal
> values" that take a literal value statement in an RDF:
>
> URI: rda:duration
> Label: Duration
> Definition: The duration of a resource
> Range rda:Duration
>
> 2. Blank node with rdf:value:
>
> R rda:duration _:x
> _:x rdf:value "29 min"
>
> Then my question was (and I don't think I got an answer): how can we
> define "Duration" such that a string like "29 min" and a more rigorous
> property definition:
>
> R rda:duration _:x
> _:x rda:hours "0"^^xsd:integer
> _:x rda:minutes "29"^^xsd:integer
>
> have the same semantics (thus retaining interoperability). I think the
> answer is that the Range can be broadly defined, and that more rigorous
> definitions must meet the "dumb down" rule (e.g. they can each be
> validly defined as "Duration" if their detail is ignored; thus the one
> above can also be expressed as "29 min").
Compare FOAF - you can choose to describe a person using the Full Name,
or split it into First/Last name, or only give an email address, etc,
etc. In all cases, the thing is an instance of foaf:Person, sometimes
blank, sometimes with a URI. So there's nothing wrong with that - it all
comes down to how we define the class rda:Duration in this case, and
that comes down to how we want to make sure we cover the important use
cases.
>
> However, I think there may be some objections that this method makes use
> of blank nodes in each case where there is no URI.
Let me very clear on this point: there is *absolutely nothing* in the
above model that prohibits you from inserting a URI in the place of _:x,
i.e.
R rda:duration <http://example.org/durations/Dur12452>
<http://example.org/durations/Dur12452> rda:hours "0"^^xsd:integer
<http://example.org/durations/Dur12452> rda:minutes "29"^^xsd:integer
So, the property definitions and even the application profile can be
*completely* silent on the issue of blank nodes if we wish.
In fact, there is no way in a property definition to even restrict a
range to blank or URI nodes. That's why I keep stating "please, let us
leave the issue of blank nodes to application developers" - it's
completely independent of the model.
/Mikael
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Plus ça change, plus c'est la même chose
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