[Crm-sig] Properties of properties in RDF

Martin Doerr martin at ics.forth.gr
Thu Mar 15 12:37:20 EET 2018

Dear Conal,

There is no conflict with adding subproperties. Once we have defined in 
FOL the logic of properties of properties, each PC class implies its 
base property. Hence, logically, the subproperty and any added ".1" will 
hold for the instances declared and imply the same base property. If, at 
any time we wish to connect term hierarchies of roles for the .1 
properties with partially declared subproperties, we need a 
straight-forward extension of the CRM. Any subproperty, e.g., may refine 
domain and range.

All the best,


On 3/15/2018 6:28 AM, Conal Tuohy wrote:
> Thanks Martin, for the link to 
> http://www.cidoc-crm.org/sites/default/files/CRMpc_v1.1_0.rdfs
> This is actually very close to (and compatible with) the approach I 
> suggested in my earlier email, and I'm embarrassed to say I wasn't 
> aware of it at all.
> I've managed to find some background material (though I had to use 
> Google to find it!)
> http://www.cidoc-crm.org/Issue/ID-266-reified-association-vs-sub-event 
> is an archive of a relevant discussion.
> http://www.cidoc-crm.org/sites/default/files/Roles.pdf presents a few 
> slides showing options for modelling properties of properties, 
> including the "Property Class" approach.
> These slides include a nice illustration of the approach defined in 
> the RDFS:
> http://www.cidoc-crm.org/sites/default/files/20160802PropertiesOfProperties.pptx
> I think I'd be very happy with this "Property Class" approach, 
> although rather than using the generic properties P01_has_domain, 
> P02_has_range, and their inverses,I would still want to define 
> specific subproperties, e.g. for the case of actors playing a specific 
> role in the performance of an activity, I would prefer to link the 
> performance (i.e. the instance of PC14 carried out by) to the actor 
> and the activity using domain-specific properties such as has_actor 
> and has_activity.
> Conal
> On 15 March 2018 at 04:25, Martin Doerr <martin at ics.forth.gr 
> <mailto:martin at ics.forth.gr>> wrote:
>     Dear All,
>     Please
>     see:http://www.cidoc-crm.org/sites/default/files/CRMpc_v1.1_0.rdfs
>     <http://www.cidoc-crm.org/sites/default/files/CRMpc_v1.1_0.rdfs>
>     on page http://www.cidoc-crm.org/versions-of-the-cidoc-crm
>     <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).
>     Best,
>     martin
>     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
>>     <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
>>     http://conaltuohy.com/
>>     @conal_tuohy
>>     +61-466-324297 <tel:0466%20324%20297>
>     -- 
>     --------------------------------------------------------------
>       Dr. Martin Doerr              |  Vox:+30(2810)391625        |
>       Research Director             |  Fax:+30(2810)391638        |
>                                     |  Email:martin at ics.forth.gr <mailto:martin at ics.forth.gr>  |
>                                                                   |
>                     Center for Cultural Informatics               |
>                     Information Systems Laboratory                |
>                      Institute of Computer Science                |
>         Foundation for Research and Technology - Hellas (FORTH)   |
>                                                                   |
>                     N.Plastira 100, Vassilika Vouton,             |
>                      GR70013 Heraklion,Crete,Greece               |
>                                                                   |
>                   Web-site:http://www.ics.forth.gr/isl            |
>     --------------------------------------------------------------
> -- 
> Conal Tuohy
> http://conaltuohy.com/
> @conal_tuohy
> +61-466-324297

  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)   |
                N.Plastira 100, Vassilika Vouton,             |
                 GR70013 Heraklion,Crete,Greece               |
              Web-site: http://www.ics.forth.gr/isl           |

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