[Crm-sig] Fwd: (no subject)

martin martin at ics.forth.gr
Mon Sep 28 18:53:26 EEST 2015


Dear Dorian,

In physics, space and time can only be separated into two independent 
dimensions when no moving
frames are involved. Even in cultural-historical data, this can happen, 
even so not frequently.
The actual place something occupies, which is identical to the "Space 
Volume" you describe, depends on the
relative movement of things and observers. They match only at an instant 
of time, but this is beyond observation, and absolute simultaneity does 
not even exist, e.g., between GPS satellites and GPS users.
Therefore,we describe now in the CRM  the "Space Volume" as a projection 
of the Spacetime volume during a time-span, which is actually a "time 
volume". The model you propose is actually in conflict with physics, 
even in a more deeper sense.

Please let me know, if this explanation is sufficiently expicit?

The problem we have discussed was not about time.

  It was a KR question:
A logical construct, which allows to state that P4 and P160 are 
identical for E4 Period and its specialization, and not two different 
properties.

Alternatively, we would for the first time in the CRM assign a property 
to two different domains, i.e., to
E2, which has no space, and to E92, which is not a phenomenon. How can 
they share an identical property?

Third alternative is, to introduce a new concept on top of E2 and E92, 
which is causal to the existence of
P160/P4. What is its nature then?

May be the problem is actually solved by a restriction of properties in 
IsA, as in:
Analyti, A., Constantopoulos, P., & Spyratos, N. (1998). Specialization 
by Restriction and Schema Derivations. /Inf.Syst./, /23/(1), 1-38, 
(03064379), (pdf <http://www.ics.forth.gr/_publications/ismodel_final.pdf>).

All the best,

Martin
>
> Dear All,
>
>
> at the last CRM-SIG meeting in Nürnberg we had a discussion on 
> Spacetime issues, especially on the usage of “*P4* has time-span” 
> and “*P160* has temporal projection”. The question of forbidding or 
> allowing *P4* to be connected with an instance of “*E4* Period” raised 
> some confusion.
>
> Even more confusion arose for me personally when I perceived the 
> absence of any “Spatial Entity”, “Space Volume” or “Time Volume” in 
> the CRM. In my humble opinion a precise modelling of Spacetime should 
> be capable of distinguishing space from time and have proper means of 
> projecting from higher-dimensional vector spaces (e.g. Spacetime 
> Volumes) to lower dimensions (e.g. Time only). Thus, an alteration and 
> extension of the CRM in the following way seems helpful:
>
>
> (X1) Introduce two concepts:
>
>
> - “*E_s* Space Volume”
>
> comprising of three-dimensional point sets that may derive their 
> identity from being the spatial extent of some material phenomena i.e. 
> the physical space where something happened, may happen, or might have 
> happened (or been present)
>
>
> - “*E_t* Time Volume”
>
> comprising of one-dimensional point sets that may derive their 
> identity from being the temporal extent of some material phenomena 
> i.e. the time (in a physical sense) when something happened, may 
> happen, or might have happened (or been present)
>
>
> (X2) Make “*E92* Spacetime Volume” a subconcept of *E_s* and of *E_t*
>
>
> (X3) Change the range of *P160*
>
> making it go from *E92 *to *E_t*instead of *E4*
>
> so that it literally projects from the Space(and)time Volume to the 
> (only)Time Volume it occupies
>
>
> (X4) Change the range of “*P**161* has spatial projection”
>
> making it go from *E92 *to*E_s *instead of “*E**53 *Place”
>
> resembling *P160*
>
>
> (X5) Change the domain of *P4*
>
> making it go from*E_t *(not *E2*) to*E52*
>
>
> (X6) Make “*E2* Temporal Entity” a subconcept of *E_t*
>
>
>
> This alteration would give us the following advantages over the 
> current model:
>
>
> (A1) There is a clear distinction between time and space whenever we 
> need it.
>
>
> (A2) the *P160* temporal projection is a true projection in the 
> meaning of a dimension reduction opposed to the datatype-kind-of 
> mapping of “*P4* has time-span”
>
> same for the *P**161* spatial projection
>
>
> (A3) the solution of the “*E4* Period, *P4* has time span XOR *P160* 
> has temporal projection”-problem: we can now use *P4* directly on 
> every Spacetime Volume i.e. also on instances of *E4*. We can, but do 
> not have to, use a temporal projection before that. However, due to 
> the projection properties (*P160* and *P**161*) applied in parallel to 
> the subClass property from Spacetime Volume to Time Volume, the 
> instantiation of such a Time Volume is only necessary, if there is a 
> need to speak about that Time Volume explicitly as separated from Space
>
>
> (A4) All that can be formulated in (relatively) lightweight 
> Description Logics and in OWL avoiding the introduction of any 
> over-sophisticated exception rules
>
>
> (maybe more)
>
>
>
> Still, open questions are:
>
>
> (Q1) Is there a (necessary) difference between *E2* Temporal Entities 
> and *E_t* Time Volumes?
>
> This should, according to my experience at the meeting, be 
> answered “yes” which raises more questions
>
>
> (Q2a) Can *E53* Places be considered Spatial Entities, which then 
> yields the analogy
>
> *E_s* Space Volume <= *E53* Spatial Entity (Place)
>
> *E_t* Time Volume <= *E2* Temporal Entity
>
>
> or
>
>
> (Q2b) Can *E53 *Places be considered 'Place Spans' so that we can 
> introduce a property “*P_p *has place” yielding the analogy
>
> *E_s *-->*P4 *has time-span**-->*E52*
>
> *E_t *-->*P_p *has place**-->*E53*
>
>
> and if not
>
>
> (Q2c) what is the distinction between “*E53* Place” and “E?? Spatial 
> Entity”?
>
>
> (Q3) Is “*E4* Period” still a subconcept of *E2* or is the inheritance 
> from “*E_t* Time Volume” via “*E92* Spacetime Volume” enough to 
> express the properties of a period?
>
>
>
> Hopefully, I have made myself clear enough to have a proper base for a 
> discussion. The attached picture shows a sketch of the described ideas 
> (Here broken arrows come from the Q-section). Please let me know about 
> your thoughts and doubts. If anyone considers it worth the effort, I 
> might also formulate some more elaborated scope notes for my 
> properties and concepts.
>
>
> With kind regards
>
> Dorian
>
>
> -------------------------------------------------------------------------------------
>
> Dipl.-Inf. Dorian Merz
> Univ. Erlangen-Nuernberg
> Department Informatik
> AG Digital Humanities
> Konrad-Zuse-Str. 3-5
> 91052 ERLANGEN
>
> Raum 00.046
> Fon: +49 9131 85 29095
> Mail: dorian.merz AT fau.de
>
>


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