[Crm-sig] Recording absence

Athanasios Velios thanasis at softicon.co.uk
Tue Nov 5 16:50:59 EET 2019

Dear all,

Following the Linked Conservation Data workshop and the last SIG in 
Crete I am summarising the problem of documenting non-existence.

An example of non-existence is: a book cover (a particular) without 
tooled decoration (a type).

Options for encoding:

1) As discussed here: 
http://lists.ics.forth.gr/pipermail/crm-sig/2012-November/001873.html , 
we could have a new E55 Type "books without decoration". This is a good 
solution but the problem is that we will need an unmanageable number of 
composite thesaurus terms to cover all possibilities, e.g. things 
without a feature, or types of events which did not happen etc.

2) In past SIGs we have mentioned negative properties. This is also a 
good solution but not quite in scope. A negative property requires 
particulars for domain and range. So I can say that:

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

This would mean that the specific book does not carry the specific 
decoration. But I want to say that the specific book does not carry any 

3) So I pestered Carlo for a few days and he says:

"To express negative information in an ontology, it is recommended to 
use specific axioms. For example, to state that certain books have no 
decorations the axiom would require to create a special class for those 
books and to make that class a sub-class of the class expression 
'individuals with less than 1 decorations'. This will require a class 
and an axiom to be created for each type of negative information to be 
expressed. But it has the advantage of using a standard OWL 2 DL 
inference engine to reason about that negative knowledge, both for 
maintaining consistency and for query answering."

So what Carlo thinks is that option 1 is reasonable and in fact instead 
of using simply a thesaurus, one should elevate these definitions to 
ontology classes and axioms.

I would be interested to hear views from the list, as I am not sure how 
to model such statements. Those of you who have looked at this in the 
past, do you get a sense of the scale for negation statements?

Thank you.


P.S. A parallel thought which did not capture Carlo's imagination was a 
"typed negative property", i.e. create new negative properties with E55 
as range as in:

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

but I am not sure how this would translate to logic in an inference engine.

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