If we are going to define an interval to mean one or the other



(1) that interval of time, or
(2) when an event occurred, e.g.  "it occurred sometime between 1964 and 2008")


The we need to go with (1), because that's how ISO 8601 defines it.


(Aside: although that itself isn't completely clear, but is "best interpretation.  And, it isn't clear that ISO 8601 has the same concept of precision as we seem to be adopting;  8601 would see 1964/2008 as meaning the interval starting at the very beginning of 1964 and ending at the very end of 2008, while we see it as the interval beginning sometime in 1964 and ending sometime in 2008. However, 8601 isn't even completely clear on that point, and I have no problem with our view.)


But look at it this way: suppose you want to say "the event occurred at some intant between 1964 and 2008".  The data element that you are saying this for could have a definition like "the interval within which the event occurred".


So as you say "you are not allowing people to unambiguously state whether they are referring to an interval or a point in time within that interval".  Is that really necessary? When you state a dateTime expression, there has to be some context, doesn't there? In other words, you are stating it as the value of a data element, right?   And the data elements definition would dictate which interpretation applies.




From: Discussion of the Developing Date/Time Standards [mailto:[log in to unmask]] On Behalf Of Simon Grant
Sent: Tuesday, July 12, 2011 2:50 AM
To: [log in to unmask]
Subject: Re: [DATETIME] interval precision


Ray, I think you've hit on a real point there.

On 11 July 2011 22:48, Denenberg, Ray <[log in to unmask]> wrote:


(1) Does it mean that interval of time, or
(2) Is it a way to represent when an event occurred, saying "it occurred sometime between 1964 and 2008".

And my understanding is that this question is out of scope, it could be either, it is a matter for the application to specify for a given data element.


Personally, I cannot see any advantage in this ambiguity. It would be really helpful if, at least, it was completely clear from the syntax whether one was referring to the whole of an interval, or to a moment in time somewhere in an interval.


Think of it like this - the way the proposal is at the moment, you are not allowing people to unambiguously state whether they are referring to an interval or a point in time within that interval. 


And it would be perfectly possible - quite easy in fact - with appropriate modifications to the spec.

Simon Grant
+44 7710031657