W3C home > Mailing lists > Public > www-rdf-calendar@w3.org > April 2001

RE: Alternative calendars and holidays, moon phases etc.

From: Jan Grant <Jan.Grant@bristol.ac.uk>
Date: Thu, 12 Apr 2001 16:51:10 +0100 (BST)
To: Charles McCathieNevile <charles@w3.org>
cc: www-rdf-calendar <www-rdf-calendar@w3.org>
Message-ID: <Pine.GSO.4.31.0104121640390.26295-100000@mail.ilrt.bris.ac.uk>
On Thu, 12 Apr 2001, Charles McCathieNevile wrote:

> On Thu, 12 Apr 2001, Jan Grant wrote:
>   On Thu, 12 Apr 2001, Charles McCathieNevile wrote:
>   > It needs a way of relating one clock to another that can be daisy-chained, so
>   > I can get from yours to mine and back.
>   I hate to say "that's a user-interface issue" - especially since that
>   sentence isn't exactly accurate; see below.
> No, I don't think it is accurate. I think it is a design decision about
> whether we want a single point of reference or whether we can do without one
> on the assumption that the distributed systems of reference will work. I
> assert that we can do the latter, and that we can then use your proposed
> single reference as just one possiblity in a distributed framework, and add
> trust semantics to the user interfaces we create that allow me to choose
> whether I trust the US navy as a keeper of that or whether I trust the
> moon-tracking machine I want to install at home one day with the clockwork
> backup, or whether I just believe my computer's clock all the time.

The point I'm trying to make is that there is a danger of
over-engineering this. There's lots of scope for complicating solutions,
but in this case it isn't necessary; if you pick a fixed point in the
past then everyone in the world will be able to agree how many seconds
have elapsed since that moment in time.

I'd say the design decision should go the other way around: do we want a
distributed system of reference for calculating time, or can we do
without that without losing any functionality by the introduciton of a
fixed point of reference that everyone can agree on. I assert the
latter, and that we can produce your proposed framework as required.
Should you wish to calculate the time of day using your moon-tracking
system, it (should be) a simple matter to work out the "real time" from
that when you wish to schedule a meeting (for example) with someone
else. Permit all sorts of timekeeping, but put the cost solely with the
ornary beggars who insist on using them :-)

Calendaring is about real life, real-world solutions. It's complicated
enough as it is!

> When people synchronise watches (see lots of old action movies...) they are
> relying on the fact that the critical timing relationships among themmselves
> are established. It may be that those are relativistic - for a far fetched
> example I might indulge in some near-light-speed travel and need to know when
> to call my Mum - but the system works either way, according to the needs that
> I describe.

The concern I have is that by the time such an over-engineered system
nears completion, relativistic travel will make this will a valid
consideration :-)

jan grant, ILRT, University of Bristol. http://www.ilrt.bris.ac.uk/
Tel +44(0)117 9287163 Fax +44 (0)117 9287112 RFC822 jan.grant@bris.ac.uk
Generalisation is never appropriate.
Received on Thursday, 12 April 2001 11:51:59 UTC

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