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Re: Question: Week Number Semantics


Frank Dawson wrote:
> The problem that I see is that a CUA's UI may wish to display "Week Number"
> in a "Week View" of the calendar. Is "Week Number" a canonical calendar
> concept that _always_ must assume Monday as the start of the week? For
> example, as is often used across multinational manufacturing corporations or
> equivalent "teaming" relationships; where a corporation's factory calendar
> is computed, based on weeks of the year.

Here in France, there comes to an agreement that MOnday is the start of
the week, and to follow the ISO numbering. For example, paper schedules
now often print the Week number in weeks views. And I expect CUAs to
offer the same, of course (and for this reason I dislike American
based products that use a different scheme for numbering).

Since I work in a company where manufacturing is primarly based on week
division, we use very often week numbers; it is common to take an 
appointment for Monday in week 23rd (even beyond the Ocean, but care is
taken when we work with -for us- foreigners).

But before in my life I worked in the IT industry, and I never heard
of week numbers there. And of course, I know that the ISO scheme is
nothing near from universal, and that in particular in the USA another
scheme is mostly used. So for example, I shall not try to take an
appointment based on week numbers with an American.

So my idea is the following: since this idea of week number is used
for specifying an appointment, I think it can be useful to be
presented at CUA level, to *take* appointment, and to display
appointments that use the same convention.

*But*, when the convention differ (the one embeeded in the appointment
vs the user-selected one), I recommend dropping the week numbers
and revert to plain vanilla Gregorian dates.

Equally, if the CUAs do not use the concept of week numbers (or the
user chose to not use it, as I did some years ago), I think the CUA
should also drop the week numbers and revert to "normal" dates.

This will be my expectations.

> Or is this a calendar concept that is sensitive to the CUA's local
> definition of "start of the week" and can yield different presentations?

I shall not recommend such an idea, as it will lead to errors.

> It would appear that if CUAs from different vendors are to be iCalendar
> "standards" based they should behave the same. Is this right?

I believe this was the original point of view of ISO8601, and therefore
why they legislated the way they did.
But experience showed that, at least in the USA (and AFAIK), another
scheme(s) kept and keep existing.
Thus, we designed iCalendar to be able to respect all cultures.
I believe this have to be kept this way.

> If so, then should we view "Week Number" as a non-permutable concept? Or
> should the display of "Week Number" vary as the "start of the week" varies?

Bottom line : I think it may vary, but varying will prevent full
interoperability on this particular topic.
Which is IMHO a small lost.