Dear all,
Wolfgang points to the fact that the 'current' properties is not defined in a
consistent way, which of course they should have been. The textual scope notes
says 'if and only if' which should be expressed as bidirectional implication, ⇔
(equivalence). Below I quite from an email exchange between Carlo and me. This
may explain the issue:
C-E:
There are several axioms in CRM of the form lefthandside(x,y)⇒
(∃z)[righthandside(x,y,z)], which is not a good thing, if I understand you
right, due to efficient machine reasoning and the time it will take to find a
needle z in the haystack.
Carlo:
Precisely. The computer enters into a combinatorial examination of cases and
basically may never come back.
and Carlo writes earlier in his reply, about claiming the existence of some
individual on the right hand side of the implication:
' it's not outside of the model, it's that we do not know what to do with it,
as you said, having a bunch of these "unknown" guys in the KB breaks
efficiency. I understand that efficiency is an engineering issue, but in the
end, we are engineers. '
In my earlier days when I worked with formal logic and models, I didn't care
very much about efficiency. However, I fully understand Carlo and also see the
point that we formulate the FOL so that it can be efficiently computable. This
is one reason to drop the bidirectional implication implication in the
properties P50, P52 and P55.
There is also another issue. The current properties P50, P52 and P55 need
external curation and also break the basic assumption that a CIDOC-CRM
KB/database store accumulate history. It would have been better if the current
properties are implemented as named and stored queries with the ting/person as
argument. The original reason for introducing the current properties was they
were used in some museum databases in the 1990ies,. Maybe it is time to get rid
of them?
Best,
Christian-Emil
P50 has current keeper
This property is a shortcut for the more detailed path from E18 Physical Thing
through, P30i custody transferred through, E10 Transfer of Custody, P29 custody
received by to E39 Actor, if and only if the custody has not been surrendered
by the receiving actor at any later time.
FOL:
P50(x,y) ⇐ (∃z) [[E10(z) ⋀ P30i(x,z) ⋀ P29(z,y) ]
⋀ ¬ (∃w) [E10(w) ⋀ P30i(x,w) ⋀ P28(w,y)⋀ P182(z,w)]]
P52 has current owner
This property is a shortcut for the more detailed path from E18 Physical Thing
through, P24i changed ownership through, E8 Acquisition, P22 transferred title
to to E39 Actor, if and only if this acquisition event is the most recent.
FOL:
P52(x,y) ⇐ (∃z) [[E8(z) ⋀ P24i(x,z) ⋀ P22(z,y) ]
⋀ ¬ (∃w) [E8(w) ⋀ P24i(x,w) ⋀ P23(w,y)⋀ P182(z,w)]]
P55 has current location
This property is a shortcut. A more detailed representation can make use of the
fully developed (i.e., indirect) path from E19 Physical Object, through, P25i
moved by, E9 Move, P26 moved to to E53 Place if and only if this Move is the
most recent.
P55(x,y) ⇐ (∃z) [ [E9(z) ⋀ P25i(x,z) ⋀ P26(z,y)]
⋀ ¬ (∃w) [E9(w) ⋀ P25i(x,w) ⋀ P27(w,y)⋀ P182(z,w)]]
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