Hi Dan, all
The recommended way to model historical periods is as instances of E4 Period. 
This recommendation is older than the introduction of E92.

The current model with E2 Temporal Entity, E52 Time-Span and E92 STV is not 
optimal and E92 is not the reason eventhough it is pretty abstract. In my 
opinion, E52 Time-Span is redundant and can be replaced by E2 Temporal Entity 
with an adjusted scope-note and change the domain of

P79 beginning is qualified by: E62 String
P80 end is qualified by: E62 String
P81 ongoing throughout: E61 Time Primitive
P82 at some time within: E61 Time Primitive
P83 had at least duration (was minimum duration of): E54 Dimension
P84 had at most duration (was maximum duration of): E54 Dimension
P160 has  temporal projection

P86 falls within (contains): E52 Time-Span can be replaced by P117 occurs 
during (includes): E2 Temporal Entity

If E52 is removed the property P160 has temporal projection should be an 
injection into E2 and have the cardinality (1,1:0,1)

(in any case: P78 is identified by (identifies) should be deprecated since E49 
Time Appellation is already deprecated.)

See also 
http://cidoc-crm.org/sites/default/files/issue%20326%20overview%20and%20thought.pptx
 for a graphical overview.

Best,
Christian-Emil

********
E2 Temporal Entity:
This class comprises all phenomena, such as the instances of E4 Periods, E5 
Events and states, which happen over a limited extent in time.  This extent in 
time must be contiguous, i.e., without gaps.  In case the defining kinds of 
phenomena for an instance of E2 Temporal Entity cease to happen, and occur 
later again at another time, we regard that the former E2 Temporal Entity has 
ended and a new instance has come into existence. In more intuitive terms, the 
same event cannot happen twice.

In some contexts, these are also called perdurants. This class is disjoint from 
E77 Persistent Item. This is an abstract class and has no direct instances. E2 
Temporal Entity is specialized into E4 Period, which applies to a particular 
geographic area (defined with a greater or lesser degree of precision), and E3 
Condition State, which applies to instances of E18 Physical Thing.


*********
E52 Time-span
This class comprises abstract temporal extents, in the sense of Galilean 
physics, having a beginning, an end and a duration. 

Time Span has no other semantic connotations. Time-Spans are used to define the 
temporal extent of instances of E4 Period, E5 Event and any other phenomena 
valid for a certain time. An E52 Time-Span may be identified by one or more 
instances of E49 Time Appellation. 

Since our knowledge of history is imperfect, instances of E52 Time-Span can 
best be considered as approximations of the actual Time-Spans of temporal 
entities. The properties of E52 Time-Span are intended to allow these 
approximations to be expressed precisely.  An extreme case of approximation, 
might, for example, define an E52 Time-Span having unknown beginning, end and 
duration. Used as a common E52 Time-Span for two events, it would nevertheless 
define them as being simultaneous, even if nothing else was known. 

Automatic processing and querying of instances of E52 Time-Span is facilitated 
if data can be parsed into an E61 Time Primitive.

*********


________________________________________
From: Crm-sig <crm-sig-boun...@ics.forth.gr> on behalf of Dan Matei 
<danmate...@gmail.com>
Sent: 19 March 2019 09:27
To: crm-sig@ics.forth.gr
Subject: Re: [Crm-sig] Space time volumes

Hi fiends,

On Mon, 18 Mar 2019 at 19:20, Martin Doerr <mar...@ics.forth.gr> wrote:

> Nevertheless, we used the term informally in the CRM. We could name E92 as 
> "abstract".

For me, some E92 are not abstract. E.g. I instantiate "Byzantine
Period" (it is somwhat difficult to place it in South America :-) :

<#ByzantinePeriod> <isA> <crm:E92_Spacetime_Volume>
<#ByzantinePeriod> <crm:P160_has_temporal_projection> <330-1700>
<#ByzantinePeriod> <crm:P161_has_spatial_projection> <#EsternEurope>
<#ByzantinePeriod> <crm:P161_has_spatial_projection> <#Levant>
<#ByzantinePeriod> <crm:P161_has_spatial_projection> <#NorthAfrica>

Also:

<#BronzeAge1> <isA> <crm:E92_Spacetime_Volume>
<#BronzeAge1> <crm:P2 has_type> <#BronzeAge-Concept>
<#BronzeAge1> <crm:P160_has_temporal_projection> <p?1>
<#BronzeAge1><crm:P161_has_spatial_projection> <#JapaneseIslands>

<#BronzeAge2> <isA> <crm:E92_Spacetime_Volume>
<#BronzeAge2> <crm:P2 has_type> <#BronzeAge-Concept>
<#BronzeAge2> <crm:P160_has_temporal_projection> <p?2>
<#BronzeAge2><crm:P161_has_spatial_projection> <#Scandinavia>

Should I worry ?

Dan
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