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; steads@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 of E92 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-bounces@ics.forth.gr> on behalf of Martin Doerr <martin@ics.forth.gr>
Sent: 12 March 2019 11:09
To: steads@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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