Subject: Simple Constraints between Events?

From: Manuel Bodirsky <[email-masked]>
Date: Sun, 21 May 2000 19:49:53 +0200

Hello,

perhaps we want to implement parts of the iCalendar+CAP-Protokoll
for our application,
but we've not found out how to implement certain things:

What we need is a kind of constraint between different events/todos,
like 'this event has to take place before that event'.
To be more precise: Two CU's, 'A' and 'B', want to fix two dates, 'I'
and 'II'. 'A' knows, that 'I' must take place before 'II'.
It's now important that he is able to let 'B' know that there is this
constraint, because 'B' might have to do some sophisticated sceduling to
fullfill this constraint.

What we don't want to do, is to let 'B' ask for a date, and
'A' simply rejects, if it violates the constraint. 
This would lead to a combinatorical explosion
when 'B' has to schedule a lot of constrained todos at several
resources.

Do we have to extend the protocol? Is it possible to extend the
protocol?

Thank you very much,
Manuel Bodirsky

---

From: "Greg FitzPatrick" <[email-masked]>
Date: Mon, 22 May 2000 12:30:29 +0200

Manuel Bodirsky wrote:

frank answers that the RELATED-TO property might fit the bill - but he
reserves himself.

In SKiCal we make clear that the RELATED-TO property is about the
relationship between calendar objects describing events and not the
relationship between the events themselves.

Therefore we have extended 2445 with

 http://www.ietf.org/internet-drafts/draft-many-ical-ski-01.txt

3.1.5   Part of another event

   Property Name: PARTOF

   Purpose: This property specifies another event, of which the
   described event is part of. This does not imply an inheritance of
   properties from the named PARTOF-event but rather a relevance.

   Value Type: TEXT. (EUID for another SKiCal/iCalendar object.)

   Property Parameters: Non-standard property parameters can be
   specified on this property. It is RECOMMENDED that a Common Name
   parameter (cnparam) be specified on this property.

   Conformance: This property CAN be specified within a "VEVENT"
   calendar component.

   Description: This property allows for the publisher of an event to
   indicate that the event is part of another event, such as a festival
   or a package of tourist attractions. This property resembles the
   RELATED-TO;RELTYPE=parent property of RFC-2445, but that property
   defines a relationship between calendar objects and not between
   events themselves.

   Format Definition: The property is defined by the following
   notation:

     partof = "PARTOF" partofparam ":" text CRLF

     partofparam  =

                   ; the following is optional,
                   ; but MUST NOT occur more than once

                   (";" languageparam ) / (";" cnparam ) /

                   ; the following is optional,
                   ; and MAY occur more than once

                   (";" xparam)
                   )

   Example: The following are examples of this property:

     PARTOF;CN=Vattenfestivalen:<[email-masked]>
     PARTOF;CN=2004 Winter Olympics:<[email-masked]>
     PARTOF:<[email-masked]>

we also describe the property relative times, which will receive a formal
description in the next version of SKiCal.

3.2.4   Relative Times

   Relative Time properties are times dependent upon the times for
   other events. They cannot exist independently.

   Example: A bus departs from the ferry terminal 20 minutes after the
   ferryboat arrives, whenever that is.

Greg