[Crm-sig] Recording absence

van Leusen, P.M. p.m.van.leusen at rug.nl
Tue Nov 5 17:36:07 EET 2019


Dear Athanasios,

this same issue came up during discussion of the ontology of archaeological
field surveying, where we wish to (and in some cases, have in fact)
recorded the absence of surface finds from a specific piece of investigated
land. A typical situation would be, that a survey team has 'walked' a field
with a particular observation intensity, say 20% (so 20% of the field's
surface has actually been inspected), and has made no archaeological finds
at all. This results in an 'empty' collection (0 finds), which is a valid
outcome just like 1, 10 or a 1000 finds would be. It was suggested by
George Bruseker to model such survey collections as Curated Holdings, but
that only works as long as there is something physical to curate - so it
does not work for 'empty' collections.
So, what solutions might be possible, analogous to the options that you've
presented here? Either we allow Curated Holdings with zero members, or we
introduce negative properties.....

Martijn


On Tue, Nov 5, 2019 at 4:03 PM Athanasios Velios <thanasis at softicon.co.uk>
wrote:

> 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
> decoration.
>
> 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.
>
> Thanasis
>
> 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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-- 
Dr. Martijn van Leusen
Associate professor, Landscape Archaeology, Groningen Institute of
Archaeology
Poststraat 6, 9712ER Groningen (Netherlands) / phone +31 50 3636717
Chair, Examination Board for Arts, Culture and Archaeology / Chair, Faculty
of Arts Advisory Board for Data Management policies
Academia page <https://rug.academia.edu/MartijnvanLeusen>
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