RE: newbie question: ical:EVENT-PROP

People,
	I've been looking at adding reminders, or alarms to events.
Having looked through the hybrid.rdf schema [1] and though the
iCalendar RFC2445 [2], I think I have the format figured.  However,
I do have some questions (and a comment) about defining alarms.

As far as I can see, here is what I *think* should be a simple alarm,
that should be triggered 30 minutes before an event start (I've omitted
start/end details for brevity):

  <ical:VEVENT rdf:ID="myEventWithReminder">
    <ical:DTSTART>
      ...
    </ical:DTSTART>

    <ical:DTEND>
      ...
    </ical:DTEND>

    <ical:VALARM-PROP>
      <ical:VALARM>
	  <ical:ACTION>DISPLAY</ical:ACTION>
	  <ical:REL-TRIGGER>
	    <ical:DURATION>
	      <rdf:value>-PT30M</rdf:value>
	    <ical:DURATION>
	  </ical:REL-TRIGGER>
	  <ical:DESCRIPTION>Reminder</ical:DESCRIPTION>
      </ical:VALARM>
    </ical:VALARM-PROP>

    <ical:DESCRIPTION> Coffee with Dana </ical:DESCRIPTION>
  </ical:VEVENT>

Now, here's the rub.  I've *guessed* that there should be an
<ical:VALARM-PROP> property, as there is no obvious property
relating a VALARM with a VEVENT.  Has this been addressed?  What
should the property be?  If it has been (accidentally omitted),
could it be added (I've appended a suggested definition at the
end of this message).

Secondly, according to [2], if the action is DISPLAY, then
the alarm must also include a DESCRIPTION property.  Ok, so I've
included one.  However, I'm not sure if I'm now breaking something
given hybrid.rdf.  Should this ontology be modified so that the
property DESCRIPTION has also the domain is also a property of
VALARM?  An alternative would be to make VALARM a subclass of a
CAL-COMPONENT, so the domain is inherited automatically...

... only, the other thing is that the comments for DESCRIPTION in
hybrid.rdf say 

  "A textual description of the CAL-COMPONENT, more complex
   than that provided by the SUMMARY property"

Would this semantic break given that the DESCRIPTION property should
be the text to be displayed when the alarm is triggered (assuming the
ACTION is DISPLAY, of course)?

And now to my comment.  I've been looking at the iCalendar output
generated by Outlook, to find (no surprise) that they almost use
it properly. Well, kind of!  If you set a reminder, then the action
is display, and the description is "Reminder" (see below).  However,
when the Outlook reminder popup appears, you see the SUMMARY text
instead.  Ok.  But more importantly, they don't seam to use the
sign of the TRIGGER correctly.  According to [2], if the trigger
is relative (i.e. a duration) then a positive duration means some
time *after* the start of the event, and a negative duration is
sometime *before* an event.  Hence in my RDF above, I have the
value -PT30M.  Yet, in the iCalendar data generated by Outlook
sets this value as positive, and fails to parse an iCalendar
description if I manually chance it to negative!  Any comments?

  BEGIN:VALARM
  TRIGGER:PT30M
  ACTION:DISPLAY
  DESCRIPTION:Reminder
  END:VALARM

Could anybody comment on whether they agree with the rdf format for
alarms, or point me in the right direction before I start creating
bad markup...
  
Thanks,

	Terry

[1] http://ilrt.org/discovery/2001/06/schemas/ical-full/hybrid.rdf
[2] http://www.ietf.org/rfc/rfc2445.txt

_____________________________________________________________________
Terry R. Payne, PhD.    | http://www.cs.cmu.edu/~terryp/index.html
CMU, Robotics Institute | Voice: (412) 268-8780 Fax: (412) 268-5569
Pittsburgh, PA 15213    | Email: terry@acm.org or Terry.Payne@cmu.edu

Received on Wednesday, 14 November 2001 23:34:02 UTC