Issue 511: Measurements and Dimensions

ID: 
511
Starting Date: 
2020-09-09
Working Group: 
3
Status: 
Open
Background: 

Posted by Robert Sanderson on 9/9/2020

Dear all,

I believe that there is an inconsistency in the model for measurements and dimensions.

E54 Dimensions are associated directly with E70 Things using P43 has dimension.  So not every class can have dimensions, only those that are descendents of E70.

However E16 Measurement's property P39 measured has a range of E1 CRM Entity, meaning that while (for example) an E53 Place cannot have a dimension, it can be measured to have a dimension. This seems inconsistent that an entity that cannot have dimensions can still be measured.

I propose that the range of P39 measured be changed to E70 Thing to resolve this inconsistency.

I would also be okay with the other direction by changing the domain of P43 has dimension to be E1 CRM Entity, however that seems like a much more significant change, and would result in quite strange side effects such as Dimensions having Dimensions.

Posted by Thanasis on 9/9/2020

Good point, but it seems to me that being able to measure a Place is pretty important. Otherwise we have to measure through the physical object/site reference or the declarative space as part of a conceptual thing.
 

Current Proposal: 

Posted by Robert on 9/9/2020

Thanks Thanasis.  Yes, there's various dimensions that are associated with non-Things, and I agree that Place is particularly easy to justify.

Place:  Area. The county of Los Angeles has a dimension of 4751 square miles. If the place is approximate, then the radius of a centroid would be an obvious dimension to record, or height/width for bounding box defined Places.

Time-Span:  Duration is already a property of a Time-Span that refers to a dimension (P191). This could then be a subproperty of P43, or deprecated in favor of a classification on the Dimension.

Temporal Entity and Spacetime Volume are a bit strange in relation to Time-Span. Does the Period have the duration or the Time-Span, or both? What if they're different

Conversely Dimensions seem like they should not have Dimensions.

Posted by Athina on 9/9/2020

As I remember, this problem was discussed in issues 229 and 307, which are declared closed. However, I am wondering, if it is related to the issue 293?

Posted by Robert on 9/9/2020

Oh, I'm sorry for duplicating your original issue 229 Athina! Great minds think alike, perhaps?

It seems like 229 was closed in favor of discussing it as part of 307, but that discussion didn't happen. 293 does seem like a good venue, but ultimately there is an inconsistency right now (as you recognized long ago!) that should not persist in version 7.0 regardless of whether ObservableEntity / Observation are moved into CRM Core or not.

Posted by Martin on 09/09/2020

On 9/9/2020 7:47 PM, Robert Sanderson wrote:

 

Oh, I'm sorry for duplicating your original issue 229 Athina! Great minds think alike, perhaps?

 

It seems like 229 was closed in favor of discussing it as part of 307, but that discussion didn't happen. 293 does seem like a good venue, but ultimately there is an inconsistency right now (as you recognized long ago!) that should not persist in version 7.0 regardless of whether ObservableEntity / Observation are moved into CRM Core or not.

I agree.

Posted by Martin on 09/09/2020

Indeed durations can be measured as distances between two events. Einstein regarded that length measurements are two simultaneous events matching both endpoints of a yardstick with something. This is the basis of the Theory of Relativity.

Basically we have to do with signals.

To be discussed!