[Crm-sig] Properties of properties in RDF
martin at ics.forth.gr
Wed Mar 14 20:25:07 EET 2018
page http://www.cidoc-crm.org/versions-of-the-cidoc-crm, plus the issues
discussing the solution for version 6.2 (I'll look for all references).
On 3/14/2018 12:49 PM, Conal Tuohy wrote:
> On 8 March 2018 at 18:02, Richard Light <richard at light.demon.co.uk
> <mailto:richard at light.demon.co.uk>> wrote:
> I was thinking last night that maybe we should focus our RDF
> efforts on exactly this issue: the representation of the CRM
> primitive classes E60, E61 and E62 in RDF. The current RDF
> document is becoming quite wide-ranging in its scope, and (for
> example) you have questioned whether certain sections belong in
> it. If we concentrate on this single aspect of the broader RDF
> issue, I think we can produce something which is of practical
> value relatively quickly. In particular, I would like to devote
> time to this during the Lyon meeting.
> I applaud the idea of focusing narrowly on something so as to produce
> some of practical value quickly!
> But I do hope that the other issues raised in that document will not
> be set aside too long, or lost.
> In particular, it seems to me that the mapping from the CRM's
> "properties of properties" to RDF is actually a more serious gap.
> In the CRM, there are a number of properties which are themselves the
> domain of properties. In RDF, however, a property does not have
> properties of its own. Incidentally, I remember years ago being able
> to model this directly in ISO Topic Maps, but practical considerations
> of interoperability and community dictate that RDF, despite its
> simpler model, is the technology of choice today.
> One example of the issue is how to model the role that individuals
> play in events. If a concert performance X was P14 carried out by
> person Y, then this maps naturally to an RDF triple in which the
> predicate is crm:P14_carried_out_by. However, if the person carried
> out that activity in a particular role (e.g. as a saxophonist) then
> things are more difficult. In the CRM, the P14_carried_out_by itself
> has the property P14.1_in_the_role_of, whose value could be an
> instance of E55_Type: Saxophonist. This is pleasingly consistent with
> how the CRM handles taxonomies in other parts of the model, but it is
> not workable in RDF because the P14_carried_out_by property cannot
> itself have a property.
> There are a number of "work-arounds" to this issue, such as simplying
> ignoring the problem and "dumbing down" the data, or moving the locus
> of classification from the property to the property value (e.g. in
> this case that would mean classifying the person rather than their
> role; that doesn't work very well because people may have many
> distinct roles, but it works better for other cases).
> The existing guidance would suggest defining a new
> "saxophone-played-by" property to be a rdfs:subpropertyof
> P14_carried_out_by. This can certainly work, but it's actually a poor
> expression of the CRM's model. It negates the practical benefits of
> having external taxonomies for this kind of classification. This
> guidance, in my opinion, makes too much of the apparent similarity
> between the CRM's properties and RDF properties. They are not in fact
> the same kind of thing, and a property which itself bears properties
> is more closely approximated in RDF not as a property but reified as a
> subject resource in its own right. A more faithful mapping of the
> CRM's abstract model to RDF would introduce a new RDFS class
> corresponding to the performance of the activity. We could then say
> that concert performance X was P14a_performed_in Performance Z; that
> Performance Z was P14b_carried_out_by person Y, and that Performance Z
> was P14.1_in_the_role_of Saxophonist.
> That's just one example of the general problem; there are a number of
> others, which are listed here in the context of the Linked Art
> project: https://github.com/linked-art/linked.art/issues/55 along with
> a variety of options for dealing with the issue.
> In my opinion the current situation with respect to properties of
> properties (in RDF) is really quite unsatisfactory and could be
> substantially improved by a more consistent treatment across the
> entire schema.
> Conal Tuohy
Dr. Martin Doerr | Vox:+30(2810)391625 |
Research Director | Fax:+30(2810)391638 |
| Email: martin at ics.forth.gr |
Center for Cultural Informatics |
Information Systems Laboratory |
Institute of Computer Science |
Foundation for Research and Technology - Hellas (FORTH) |
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Web-site: http://www.ics.forth.gr/isl |
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