Subject: [IPTEL] An annoying case for CPL time-switch

From: Jonathan Lennox <[email-masked]>
Date: Thu, 17 May 2001 13:50:01 -0400 (EDT)

Something annoying just occured to me for CPL's time-switch, while I was
writing up a comment for the CalSch list.

We've been assuming you can treat iCalendar's EXRULE/EXDATE as an additional
time-switch output.  However, consider the following (plausible) scenario.

1.  The base rule is "Between 9 and 5, anyone can ring at my desk.  Outside
of that time, this group of people are allowed to call my cel phone."  So
far so good.  Call these time-switch rules 3 and 4 (where 4 is an
<otherwise>.)

2.  You add a rule (listed before this) saying "I have a very important
meeting between 4 and 6 every Wednesday; during this time, no one is allowed
to reach me at all."  Again, so far so good; this just gets listed as an
earlier rule in the time-switch.  Call this time-switch rule 2.

3.  "On Wednesday, May 23, 2001, the special meeting is canceled, so on that
particular day my regular rules should resume."  Call this rule 1 -- but
what should it be?

What we want in this case is a way to be able to say that rule 1 should
cause rule 2 to be jumped over, continuing with 3 and 4.

One, moderately ugly, solution would be implement this as a cascaded
sequence of <time-switch> nodes and subs, looking like
<sub foo>
  <time-switch>
    <time rule3> [desk] </time>
    <otherwise> [celphone] </otherwise>
  </ts>
</sub>

<incoming>
  <time-switch>
    <time rule1> <sub foo /> </time>
    <time rule2> [voicemail] </time>
    <otherwise> <sub foo /> </time>
  </ts>
</inc>

Even worse, we could split rule1 into rule1a and rule1b, reflecting the
intersections of rule1 with rule3 and rule4 respectively.  This is, however,
awful (and probably not generally possible).

Is it okay if we say that EXDATE and EXRULE should always get translated
into time-switches of the sub-output-sub form?  Or do we need some explicit
way of letting one rule force us to "jump over" subsequent rules?

-- 
Jonathan Lennox
[email-masked]

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From: James Undery <[email-masked]>
Date: Fri, 18 May 2001 08:36:52 +0100

>     <otherwise> <sub foo /> </time>

It might be a matter of style but I think this solution isn't that ugly, just
inefficient

<incoming>
    <time-switch>
        <time rule 2>
            <time-switch>
                <time rule1> <sub foo /> </time>
                <otherwise> [voicemail] </otherwise>
            </time-switch>
        </time>
        <otherwise> <sub foo /> </otherwise>
    </time-switch>
</incoming>

is more efficient but ugly.

> way of letting one rule force us to "jump over" subsequent rules?

I can't see the problem here and think "jumping over" rules is worse, subactions
are the best solution IMO.

James Undery