Dear Christian-Emil, All,
Thank you for your explanations. I agree with you technically completely.
I propose to have cardinality (1,1:0,1) for P4 and P160.
The scope note of P4 must be modified, as you say. We have discussed
already, that alternative opinions are questions of the knowledge base,
and not of the ontology.
I only disagree :-) with:
"The model will .... and hopefully be more intuitive for the lay
persons." with the additional link:
Firstly, I have made the argument, and got no response, that introducing
a link between E4 and E92 does *not* solve the problem of equivalence of
P4 and P160. It is still exactly the same, only *more *complex to
formulate: we have to equate a path with a single link.
Secondly, the lay person will see a knowledge graph of instances, and
not a theory. A knowledge graph with a lot of trivial links in my
opinion makes the model less intuitive to *use*. Moreover, all our RDF
databases are still very bad following links. Any additional join has
high cost. Still, most CRM implementations materialize a huge number of
paths to increase performance.
.......
I still do not see, why we should reduce performance because we find it
difficult to explain the theory;-)
Basically, as you say, we repeat old arguments here, long before
decided, without new insight.
Best,
Martin
On 3/12/2019 5:04 PM, Christian-Emil Smith Ore wrote:
I resend the email, without the long tail of the previous emails due
to length restrictions.
Best
Christian-Emil
------------------------------------------------------------------------
*From:* Christian-Emil Smith Ore
*Sent:* 12 March 2019 15:24
*To:* Martin Doerr; ste...@paveprime.com; 'George Bruseker'
*Cc:* 'crm-sig'
*Subject:* Re: [Crm-sig] Issue 326 Resolving inconsistencies between
E2, E4, E52 and E92
Dear all,
The issue 326 is old. I made some slides (dated 31/3/2017) which can
be found at
http://www.edd.uio.no/download/cidoc_crm/issue-326-overview-and-thoughts-HW.pptx
The exchange of emails has two topics:
1) E18 Physical Thing as a subclass of E92 Spacetime Volume
2) the properties P4 and P160
**********
1: In my opinion it is model theoretically correct that E18 Physical
Thing as a subclass ofE92 Spacetime Volume. However, it may
be confusing for persons not so interested in theory. Therefor we
could introduce a property Pxx E18 Physical Thing <-> E92
Spacetime Volume with the cardinality (1,1:0,1) describing the the
(model theoretical) fact that a part of E18 Physical Thing is in a
1-1 correspondence with a subset of E92 Spacetime Volume.
The model will still have the same explanatory power, and hopefully be
more intuitive for the lay persons.
***********
2:
In the slides I give the following comment:
"The cardinality of P4 has time-span is (1,1:1,n), that is, two or
more instances of E2 Temporal Entity can “share” an instance of E52
Time-span. This was introduced in an early stage to model simultaneity.
This way of modeling simultaneity is considered obsolete and the
cardinality of P4 should be (1,1:1,1)-
E2 Temporal Entity and E52 Time-span in a one to one relation
E2 Temporal Entity and E92 Spacetime Volume in a one to one relation. "
Please, note that P4's cardinality states that every instance of P4
is connected to one and only one instance of E52 Time-span. Therefore,
the number of instances of E52 Time-span will be equal or less than
the number of instances of E2 Temporal Entity.
The number of instance of E92 Spacetime Volume and E2 Temporal Entity
will always be equal due to the cardinality (1,1:1,1) of P160 has
temporal projection. E4 Period is a subclass of E92 Spacetime Volume
and has less than or equal number of instances. The cardinality of
P160 when lowered to
P160: E4 Period <-> E52 Time-span
must have the more strict cardinality (1,1:0,1), that is, it is an
injection of E4 Period into E52 Time-span. There may exist instances
of E52 Time-span which are not related to an instance of the subclass
E4 Period
Correspondingly:
P4: E4 Period <-> E52 Time-span
must have the cardinality constraint (1,1:0,n).
The scope note of P160:
“This property describes the temporal projection of an instance of an
E92 Spacetime Volume. The property P4 has time-span is the same as
P160 has temporal projection if it is used to document an instance of
E4 Period or any subclass of it.”
So the formulation discussed in the emails is already there.
The scope note of P4:
“This property describes the temporal confinement of an instance of
an E2 Temporal Entity. The related E52 Time-Span is understood as the
real Time-Span during which the phenomena were active, which make up
the temporal entity instance. It does not convey any other meaning
than a positioning on the “time-line” of chronology. The Time-Span in
turn is approximated by a set of dates (E61 Time Primitive). A
temporal entity can have in reality only one Time-Span, but there may
exist alternative opinions about it, which we would express by
assigning multiple Time-Spans. Related temporal entities may share a
Time-Span. Time-Spans may have completely unknown dates but other
descriptions by which we can infer knowledge.”
The formulation “A temporal entity can have in reality only one
Time-Span, but there may exist alternative opinions about it, which we
would express by assigning multiple Time-Spans.” should be deleted.
Such multiple assignment due to uncertainties or alternative opinions
is the case for many properties in CRM.
In my opinion “Related temporal entities may share a Time-Span.”
should also be deleted and the cardinality of P4 (E2 Temporal Entity
<-> E52 Time-span) made stricter to (1,1:1,1).
Best,
Christian-Emil
------------------------------------------------------------------------
*From:* Crm-sig <crm-sig-boun...@ics.forth.gr> on behalf of Martin
Doerr <mar...@ics.forth.gr>
*Sent:* 12 March 2019 11:09
*To:* ste...@paveprime.com; 'George Bruseker'
*Cc:* 'crm-sig'
*Subject:* Re: [Crm-sig] Issue 326 Resolving inconsistencies between
E2, E4, E52 and E92
Dear Steve, George,
Your arguments well taken, I may remind you that the argument was not
only a 1:1 relation.
It contained 4 elements:
a) a 1:1 relation
b) a common identity condition: The identity of the STV depends on the
identity of the phenomenon
c) There existence conditions are identical: the one exists where and
as long as the other
d) Properties do not interfere.
The condition d) becomes more tricky with the question of the time
spans, as you have seen. Here, the question for me is not ontological,
but of the logical formalism. As I have shown, it can be described in
FOL. It is the only complication we have. We just declare two
properties to be identical downwards.
The alternative you are advocating for is:
a) Fill the database with a very large number of necessary 1:1 links:
events are some of the the most frequent items we have.
b) You have not solved anything wrt P160, because P4 is still the same
as P160 in these cases, and the path of correspondence is even more
confusing.
So, we just buy in a much more confusing schema, to my opinion. The
schema is what we use on a daily base. Discussing CRM extensions is
not the end-users interest, but the task of the SIG.
I believe we cannot avoid entering some complexity here in our
discussions, and resolve it giving priority to the end-user schema.
I think the first arguments should be, if the final schema is
confusing, and if the alternative is less confusing.
I am not sure where to publish adequately the above reasoning. It
should be somewhere buried in the minutes. But we tried very hard to
make the things clear in the scope notes of E4, E18.
What do you think?
All the best,
Martin
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--
------------------------------------
Dr. Martin Doerr
Honorary Head of the
Center for Cultural Informatics
Information Systems Laboratory
Institute of Computer Science
Foundation for Research and Technology - Hellas (FORTH)
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