Recording absence

The reference to Manuscript 1 from the Ligatus condition survey form is indicative of this issue which appears in many other examples.

It is important to document that an object does NOT consist of a material or a component, or does not have a characteristic. For example: a book cover without tooled decoration.

Solution 1:
In November 2012, this was discussed in the SIG:
http://lists.ics.forth.gr/pipermail/crm-sig/2012-November/001873.html
And the response was that objects without a characteristic can be expressed using E55 Type, for example “cover without decoration” is a narrower term of “cover”. This would mean that a thesaurus would need to include hundreds/thousands of composite terms to cover the possible non-existent features of things. I do not believe this is a viable solution.

Solution 2:
We can use 0 number on P57 has number of parts, which is not really a good solution as we will need to create a URI for something that does not exist.
Solution 3:
Carlo and Martin have discussed the use of negative CRM properties, but I do not have a reference or guidelines for implementation in RDF. Perhaps the above example would be:

cover(E22 Human-Made Object) →NOT P56 bears feature →tooled decoration(E25 Human-Made Feature)

But this would pose two problems:
tooled decoration(E25 Human-Made Feature) would require a URI, but it is not a thing.
NOT P56 bears feature would require an additional property (plus its negative inverse) in the rdfs definition.
Alternatively this structure should be:

cover(E22 Human-Made Object) →NOT P56 bears feature →tooled decoration(E55 Type)

It may be that all negative properties require either literals or E55 Type as range.

TODO

  • check which CRM properties can be negative and what will their ranges be
  • Formalise negative properties in the rdfs representation of the CRM

Relevant links
OWL: https://www.w3.org/2007/OWL/wiki/FullSemanticsNegativePropertyAssertions
Current discussion in CRM-SIG list: http://lists.ics.forth.gr/pipermail/crm-sig/2019-December/004108.html
Presentation at CRM-SIG September 2019: https://www.slideshare.net/avelios/linked-conservation-data-crmsig-prese...