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RE: OWL-Time extensions for Era

From: Little, Chris <chris.little@metoffice.gov.uk>
Date: Tue, 21 Jul 2020 12:17:06 +0000
To: "Cox, Simon (L&W, Clayton)" <Simon.Cox@csiro.au>, Élie Roux <elie.roux@telecom-bretagne.eu>
CC: "public-sdwig@w3.org" <public-sdwig@w3.org>
Message-ID: <CWXP265MB0053FD71FA7335D4CCDB2382A7780@CWXP265MB0053.GBRP265.PROD.OUTLOOK.COM>

I am very wary of adding a few properties " so that some arithmetic can be performed ". 

Do you mean integer arithmetic only? Or do you need rational or real numbers as well? If there is a logically underlying coordinate reference system, no problem. And calendars, which are not coordinate reference systems, have all sorts of 'special' arithmetic. The missing year '0' between CE and BCE is perhaps the simplest example. 

However, if one has constructed a temporal reference system based on, say, reigns of rulers such as Pharoahs, or sets of tree rings or ice cores, it is a logical mistake to infer that (correct) arithmetic can be performed. There may be gaps or overlaps in the historical record such as interregnums.

-----Original Message-----
From: Cox, Simon (L&W, Clayton) <Simon.Cox@csiro.au> 
Sent: 21 July 2020 05:44
To: Élie Roux <elie.roux@telecom-bretagne.eu>
Cc: public-sdwig@w3.org
Subject: RE: OWL-Time extensions for Era

I recall many threads on this through the years. 
I don't have time to track down chapter and verse at the moments, but believe the outcome is - there was no year 0 ! i.e. the calendar went straight from -1 to 1. 
i.e. it is a nominal not an ordinal ... and you have to use special arithmetic to compute durations that span the change. 

> -----Original Message-----
> From: Élie Roux <elie.roux@telecom-bretagne.eu>
> Sent: Monday, 20 July, 2020 18:56
> To: Cox, Simon (L&W, Clayton) <Simon.Cox@csiro.au>
> Cc: public-sdwig@w3.org
> Subject: Re: OWL-Time extensions for Era
> As a side note, if the common era is an interval, when does it start?
> beginning of year 1 of beginning of year 0?
> Some eras do start at year number 0 (like Kali Yuga), some at year 
> number 1 (most regnal years eras). Do you think we should have some 
> property about that so that some arithmetic can be performed?
> Best,
> --
> Elie

Received on Tuesday, 21 July 2020 12:17:21 UTC

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