Subject: Re: Ahn's message on temporal element

From: [email-masked]
Date: Wed, 15 Sep 1993 07:02:23 MST

From: Shashi K. Gadia <[email-masked]>
	Subject: Ahn's message on temporal element
	To: [email-masked]
	Date: Tue, 14 Sep 93 14:36:17 CDT
	
	A temporal element in one dimension is 
	a union but NOT a set of intervals.  

Greetings.
If a union is a set operator, doesn't a union of intervals
result in a set (of intervals) ?
I don't see the significance of the distinction here.

	The terms "Multi-intervals" or "Interval sets" 
	or simply "Intervals" lean towards a set and 
	not union.  

I don't see how "temporal element" denotes a union better,
if a distinction between a set and a union is important.
	
	The term temporal element is more generic.  
	In the bitemporal model, it is union of rectangles.  
	Moreover if your bitemporal space does not contain 
	notion of future the bitemporal space reduces 
	to triangle below the diagonal.  And a temporal 
	element becomes union of triangles and rectangles.  
	(See Section 6.2 on page P-26 of workshop 
	proceedings.)

Term "interval" is used in a general sense too.
For example, Section 3.15 mentions bitemporal intervals.
	
	The term temporal element generalizes to spatial 
	or spatio-temporal element.  A spatio temporal 
	element can be very complex. 
	
A temporal element reminds me of a picture element, which is a pixel.
This unintended similarity may become more significant
in a spatio-temporal DB which may deal with images.

Regards
Ilsoo Ahn