Subject: [IPTEL] CPL: time-switch recurrence rules

From: Jonathan Lennox <[email-masked]>
Date: Wed, 12 Jul 2000 17:09:58 -0400 (EDT)

The -01 CPL specification gives some rather simple rules for how to specify
a time interval for routing calls.  It's been suggested to me that we use
instead the very complex and powerful iCalendar (RFC 2445) syntax for time
intervals instead, as a) this is an already established IANA standard for
this sort of thing, and b) being able to create a CPL automatically based on
one's calendar entries would be very useful.

The problem is that iCal timezone rules are remarkably complicated things;
I've included the RRULE examples section of RFC 2445 at the end of this
message to give a feel for this.  Do people feel that the added expressive
power and compatibility of iCal is worth the additional complexity this
imposes on server and script writers?  And to what extent should this syntax
be mapped into XML, vs. being used directly?

-- 
Jonathan Lennox
[email-masked]
   Example: All examples assume the Eastern United States time zone.

   Daily for 10 occurrences:

     DTSTART;TZID=US-Eastern:19970902T090000
     RRULE:FREQ=DAILY;COUNT=10

     ==> (1997 9:00 AM EDT)September 2-11

   Daily until December 24, 1997:

     DTSTART;TZID=US-Eastern:19970902T090000
     RRULE:FREQ=DAILY;UNTIL=19971224T000000Z

     ==> (1997 9:00 AM EDT)September 2-30;October 1-25
         (1997 9:00 AM EST)October 26-31;November 1-30;December 1-23

   Every other day - forever:

     DTSTART;TZID=US-Eastern:19970902T090000
     RRULE:FREQ=DAILY;INTERVAL=2
     ==> (1997 9:00 AM EDT)September2,4,6,8...24,26,28,30;
          October 2,4,6...20,22,24
         (1997 9:00 AM EST)October 26,28,30;November 1,3,5,7...25,27,29;
          Dec 1,3,...

   Every 10 days, 5 occurrences:

     DTSTART;TZID=US-Eastern:19970902T090000
     RRULE:FREQ=DAILY;INTERVAL=10;COUNT=5

     ==> (1997 9:00 AM EDT)September 2,12,22;October 2,12

   Everyday in January, for 3 years:

     DTSTART;TZID=US-Eastern:19980101T090000
     RRULE:FREQ=YEARLY;UNTIL=20000131T090000Z;
      BYMONTH=1;BYDAY=SU,MO,TU,WE,TH,FR,SA
     or
     RRULE:FREQ=DAILY;UNTIL=20000131T090000Z;BYMONTH=1

     ==> (1998 9:00 AM EDT)January 1-31
         (1999 9:00 AM EDT)January 1-31
         (2000 9:00 AM EDT)January 1-31

   Weekly for 10 occurrences

     DTSTART;TZID=US-Eastern:19970902T090000
     RRULE:FREQ=WEEKLY;COUNT=10

     ==> (1997 9:00 AM EDT)September 2,9,16,23,30;October 7,14,21
         (1997 9:00 AM EST)October 28;November 4

   Weekly until December 24, 1997

     DTSTART;TZID=US-Eastern:19970902T090000
     RRULE:FREQ=WEEKLY;UNTIL=19971224T000000Z

     ==> (1997 9:00 AM EDT)September 2,9,16,23,30;October 7,14,21
         (1997 9:00 AM EST)October 28;November 4,11,18,25;
                           December 2,9,16,23
   Every other week - forever:

     DTSTART;TZID=US-Eastern:19970902T090000
     RRULE:FREQ=WEEKLY;INTERVAL=2;WKST=SU

     ==> (1997 9:00 AM EDT)September 2,16,30;October 14
         (1997 9:00 AM EST)October 28;November 11,25;December 9,23
         (1998 9:00 AM EST)January 6,20;February
     ...

   Weekly on Tuesday and Thursday for 5 weeks:

    DTSTART;TZID=US-Eastern:19970902T090000
    RRULE:FREQ=WEEKLY;UNTIL=19971007T000000Z;WKST=SU;BYDAY=TU,TH
    or
    RRULE:FREQ=WEEKLY;COUNT=10;WKST=SU;BYDAY=TU,TH

    ==> (1997 9:00 AM EDT)September 2,4,9,11,16,18,23,25,30;October 2

   Every other week on Monday, Wednesday and Friday until December 24,
   1997, but starting on Tuesday, September 2, 1997:

     DTSTART;TZID=US-Eastern:19970902T090000
     RRULE:FREQ=WEEKLY;INTERVAL=2;UNTIL=19971224T000000Z;WKST=SU;
      BYDAY=MO,WE,FR
     ==> (1997 9:00 AM EDT)September 2,3,5,15,17,19,29;October
     1,3,13,15,17
         (1997 9:00 AM EST)October 27,29,31;November 10,12,14,24,26,28;
                           December 8,10,12,22

   Every other week on Tuesday and Thursday, for 8 occurrences:

     DTSTART;TZID=US-Eastern:19970902T090000
     RRULE:FREQ=WEEKLY;INTERVAL=2;COUNT=8;WKST=SU;BYDAY=TU,TH

     ==> (1997 9:00 AM EDT)September 2,4,16,18,30;October 2,14,16

   Monthly on the 1st Friday for ten occurrences:

     DTSTART;TZID=US-Eastern:19970905T090000
     RRULE:FREQ=MONTHLY;COUNT=10;BYDAY=1FR

     ==> (1997 9:00 AM EDT)September 5;October 3
         (1997 9:00 AM EST)November 7;Dec 5
         (1998 9:00 AM EST)January 2;February 6;March 6;April 3
         (1998 9:00 AM EDT)May 1;June 5

   Monthly on the 1st Friday until December 24, 1997:

     DTSTART;TZID=US-Eastern:19970905T090000
     RRULE:FREQ=MONTHLY;UNTIL=19971224T000000Z;BYDAY=1FR

     ==> (1997 9:00 AM EDT)September 5;October 3
         (1997 9:00 AM EST)November 7;December 5

   Every other month on the 1st and last Sunday of the month for 10
   occurrences:

     DTSTART;TZID=US-Eastern:19970907T090000
     RRULE:FREQ=MONTHLY;INTERVAL=2;COUNT=10;BYDAY=1SU,-1SU

     ==> (1997 9:00 AM EDT)September 7,28
         (1997 9:00 AM EST)November 2,30
         (1998 9:00 AM EST)January 4,25;March 1,29
         (1998 9:00 AM EDT)May 3,31

   Monthly on the second to last Monday of the month for 6 months:

     DTSTART;TZID=US-Eastern:19970922T090000
     RRULE:FREQ=MONTHLY;COUNT=6;BYDAY=-2MO

     ==> (1997 9:00 AM EDT)September 22;October 20
         (1997 9:00 AM EST)November 17;December 22
         (1998 9:00 AM EST)January 19;February 16

   Monthly on the third to the last day of the month, forever:

     DTSTART;TZID=US-Eastern:19970928T090000
     RRULE:FREQ=MONTHLY;BYMONTHDAY=-3

     ==> (1997 9:00 AM EDT)September 28
         (1997 9:00 AM EST)October 29;November 28;December 29
         (1998 9:00 AM EST)January 29;February 26
     ...

   Monthly on the 2nd and 15th of the month for 10 occurrences:

     DTSTART;TZID=US-Eastern:19970902T090000
     RRULE:FREQ=MONTHLY;COUNT=10;BYMONTHDAY=2,15

     ==> (1997 9:00 AM EDT)September 2,15;October 2,15
         (1997 9:00 AM EST)November 2,15;December 2,15
         (1998 9:00 AM EST)January 2,15

   Monthly on the first and last day of the month for 10 occurrences:

     DTSTART;TZID=US-Eastern:19970930T090000
     RRULE:FREQ=MONTHLY;COUNT=10;BYMONTHDAY=1,-1

     ==> (1997 9:00 AM EDT)September 30;October 1
         (1997 9:00 AM EST)October 31;November 1,30;December 1,31
         (1998 9:00 AM EST)January 1,31;February 1

   Every 18 months on the 10th thru 15th of the month for 10
   occurrences:

     DTSTART;TZID=US-Eastern:19970910T090000
     RRULE:FREQ=MONTHLY;INTERVAL=18;COUNT=10;BYMONTHDAY=10,11,12,13,14,
      15

     ==> (1997 9:00 AM EDT)September 10,11,12,13,14,15
         (1999 9:00 AM EST)March 10,11,12,13

   Every Tuesday, every other month:

     DTSTART;TZID=US-Eastern:19970902T090000
     RRULE:FREQ=MONTHLY;INTERVAL=2;BYDAY=TU

     ==> (1997 9:00 AM EDT)September 2,9,16,23,30
         (1997 9:00 AM EST)November 4,11,18,25
         (1998 9:00 AM EST)January 6,13,20,27;March 3,10,17,24,31
     ...

   Yearly in June and July for 10 occurrences:

     DTSTART;TZID=US-Eastern:19970610T090000
     RRULE:FREQ=YEARLY;COUNT=10;BYMONTH=6,7
     ==> (1997 9:00 AM EDT)June 10;July 10
         (1998 9:00 AM EDT)June 10;July 10
         (1999 9:00 AM EDT)June 10;July 10
         (2000 9:00 AM EDT)June 10;July 10
         (2001 9:00 AM EDT)June 10;July 10
     Note: Since none of the BYDAY, BYMONTHDAY or BYYEARDAY components
     are specified, the day is gotten from DTSTART

   Every other year on January, February, and March for 10 occurrences:

     DTSTART;TZID=US-Eastern:19970310T090000
     RRULE:FREQ=YEARLY;INTERVAL=2;COUNT=10;BYMONTH=1,2,3

     ==> (1997 9:00 AM EST)March 10
         (1999 9:00 AM EST)January 10;February 10;March 10
         (2001 9:00 AM EST)January 10;February 10;March 10
         (2003 9:00 AM EST)January 10;February 10;March 10

   Every 3rd year on the 1st, 100th and 200th day for 10 occurrences:

     DTSTART;TZID=US-Eastern:19970101T090000
     RRULE:FREQ=YEARLY;INTERVAL=3;COUNT=10;BYYEARDAY=1,100,200

     ==> (1997 9:00 AM EST)January 1
         (1997 9:00 AM EDT)April 10;July 19
         (2000 9:00 AM EST)January 1
         (2000 9:00 AM EDT)April 9;July 18
         (2003 9:00 AM EST)January 1
         (2003 9:00 AM EDT)April 10;July 19
         (2006 9:00 AM EST)January 1

   Every 20th Monday of the year, forever:

     DTSTART;TZID=US-Eastern:19970519T090000
     RRULE:FREQ=YEARLY;BYDAY=20MO

     ==> (1997 9:00 AM EDT)May 19
         (1998 9:00 AM EDT)May 18
         (1999 9:00 AM EDT)May 17
     ...

   Monday of week number 20 (where the default start of the week is
   Monday), forever:

     DTSTART;TZID=US-Eastern:19970512T090000
     RRULE:FREQ=YEARLY;BYWEEKNO=20;BYDAY=MO

     ==> (1997 9:00 AM EDT)May 12
         (1998 9:00 AM EDT)May 11
         (1999 9:00 AM EDT)May 17
     ...

   Every Thursday in March, forever:

     DTSTART;TZID=US-Eastern:19970313T090000
     RRULE:FREQ=YEARLY;BYMONTH=3;BYDAY=TH

     ==> (1997 9:00 AM EST)March 13,20,27
         (1998 9:00 AM EST)March 5,12,19,26
         (1999 9:00 AM EST)March 4,11,18,25
     ...

   Every Thursday, but only during June, July, and August, forever:

     DTSTART;TZID=US-Eastern:19970605T090000
     RRULE:FREQ=YEARLY;BYDAY=TH;BYMONTH=6,7,8

     ==> (1997 9:00 AM EDT)June 5,12,19,26;July 3,10,17,24,31;
                       August 7,14,21,28
         (1998 9:00 AM EDT)June 4,11,18,25;July 2,9,16,23,30;
                       August 6,13,20,27
         (1999 9:00 AM EDT)June 3,10,17,24;July 1,8,15,22,29;
                       August 5,12,19,26
     ...

   Every Friday the 13th, forever:

     DTSTART;TZID=US-Eastern:19970902T090000
     EXDATE;TZID=US-Eastern:19970902T090000
     RRULE:FREQ=MONTHLY;BYDAY=FR;BYMONTHDAY=13

     ==> (1998 9:00 AM EST)February 13;March 13;November 13
         (1999 9:00 AM EDT)August 13
         (2000 9:00 AM EDT)October 13
     ...

   The first Saturday that follows the first Sunday of the month,
    forever:

     DTSTART;TZID=US-Eastern:19970913T090000
     RRULE:FREQ=MONTHLY;BYDAY=SA;BYMONTHDAY=7,8,9,10,11,12,13

     ==> (1997 9:00 AM EDT)September 13;October 11
         (1997 9:00 AM EST)November 8;December 13
         (1998 9:00 AM EST)January 10;February 7;March 7
         (1998 9:00 AM EDT)April 11;May 9;June 13...
     ...

   Every four years, the first Tuesday after a Monday in November,
   forever (U.S. Presidential Election day):

     DTSTART;TZID=US-Eastern:19961105T090000
     RRULE:FREQ=YEARLY;INTERVAL=4;BYMONTH=11;BYDAY=TU;BYMONTHDAY=2,3,4,
      5,6,7,8

     ==> (1996 9:00 AM EST)November 5
         (2000 9:00 AM EST)November 7
         (2004 9:00 AM EST)November 2
     ...

   The 3rd instance into the month of one of Tuesday, Wednesday or
   Thursday, for the next 3 months:

     DTSTART;TZID=US-Eastern:19970904T090000
     RRULE:FREQ=MONTHLY;COUNT=3;BYDAY=TU,WE,TH;BYSETPOS=3

     ==> (1997 9:00 AM EDT)September 4;October 7
         (1997 9:00 AM EST)November 6

   The 2nd to last weekday of the month:

     DTSTART;TZID=US-Eastern:19970929T090000
     RRULE:FREQ=MONTHLY;BYDAY=MO,TU,WE,TH,FR;BYSETPOS=-2

     ==> (1997 9:00 AM EDT)September 29
         (1997 9:00 AM EST)October 30;November 27;December 30
         (1998 9:00 AM EST)January 29;February 26;March 30
     ...

   Every 3 hours from 9:00 AM to 5:00 PM on a specific day:

     DTSTART;TZID=US-Eastern:19970902T090000
     RRULE:FREQ=HOURLY;INTERVAL=3;UNTIL=19970902T170000Z

     ==> (September 2, 1997 EDT)09:00,12:00,15:00

   Every 15 minutes for 6 occurrences:

     DTSTART;TZID=US-Eastern:19970902T090000
     RRULE:FREQ=MINUTELY;INTERVAL=15;COUNT=6

     ==> (September 2, 1997 EDT)09:00,09:15,09:30,09:45,10:00,10:15

   Every hour and a half for 4 occurrences:

     DTSTART;TZID=US-Eastern:19970902T090000
     RRULE:FREQ=MINUTELY;INTERVAL=90;COUNT=4

     ==> (September 2, 1997 EDT)09:00,10:30;12:00;13:30

   Every 20 minutes from 9:00 AM to 4:40 PM every day:

     DTSTART;TZID=US-Eastern:19970902T090000
     RRULE:FREQ=DAILY;BYHOUR=9,10,11,12,13,14,15,16;BYMINUTE=0,20,40
     or
     RRULE:FREQ=MINUTELY;INTERVAL=20;BYHOUR=9,10,11,12,13,14,15,16

     ==> (September 2, 1997 EDT)9:00,9:20,9:40,10:00,10:20,
                                ... 16:00,16:20,16:40
         (September 3, 1997 EDT)9:00,9:20,9:40,10:00,10:20,
                               ...16:00,16:20,16:40
     ...

   An example where the days generated makes a difference because of
   WKST:

     DTSTART;TZID=US-Eastern:19970805T090000
     RRULE:FREQ=WEEKLY;INTERVAL=2;COUNT=4;BYDAY=TU,SU;WKST=MO

     ==> (1997 EDT)Aug 5,10,19,24

     changing only WKST from MO to SU, yields different results...

     DTSTART;TZID=US-Eastern:19970805T090000
     RRULE:FREQ=WEEKLY;INTERVAL=2;COUNT=4;BYDAY=TU,SU;WKST=SU
     ==> (1997 EDT)August 5,17,19,31

---

From: Jonathan Rosenberg <[email-masked]>
Date: Thu, 13 Jul 2000 01:25:11 -0400

I'm inclined to say no.

We are not solving the same problem. In CPL, we are not looking to
schedule events, but rather to describe times during which different
call processing actions take place. I expect that if a user wants to
have calls blocked from 2-4 pm until next Wed., they would simply change
their CPL next Wed, for example. 

The current format in the cpl draft allows for the most common cases,
which is time of day filtering (all calls go home after 5pm), and day of
week (send to voicemail on weekends). In the interests of KISS, I'd
rather stick to the simpler stuff.

-Jonathan R.

Jonathan Lennox wrote:
>   ------------------------------------------------------------------------

-- 
Jonathan D. Rosenberg                       72 Eagle Rock Ave.
Chief Scientist                             First Floor
dynamicsoft                                 East Hanover, NJ 07936
[email-masked]                     FAX:   (973) 952-5050
http://www.cs.columbia.edu/~jdrosen         PHONE: (732) 741-7244
http://www.dynamicsoft.com

_______________________________________________
IPTEL mailing list
[email-masked]
http://lists.bell-labs.com/mailman/listinfo/iptel

---

From: Henning Schulzrinne <[email-masked]>
Date: Wed, 12 Jul 2000 17:23:27 -0400

> be mapped into XML, vs. being used directly?

I don't see this as being that different in complexity from the
"crontab" style specification. Basically, there's a start time, stop
time, a repeat interval and some day/hour/month lists. The only major
difference (besides start and stop times and a count) seems to be the
specification of FREQ, rather than the implied version by listing ranges
or lists for days, etc.

The "or" would have to be modeled appropriately - is this feasible
within the existing switch mechanism? Presumably one could always repeat
whatever the switch enclosed.

I would find a mapping to XML parameters slightly cleaner (and less work
in parsing), as long as all the parameters can be readily encoded as
comma-lists in ""-enclosed parameters. Something like

freq="weekly" until="19971007T000000Z" wkst="su" byday="tu,th"

I think one test of the complexity might be to write down pseudocode to
check a particular time against such a rule. 

-- 
Henning Schulzrinne   http://www.cs.columbia.edu/~hgs

---

From: Henning Schulzrinne <[email-masked]>
Date: Thu, 13 Jul 2000 09:28:13 -0400

> their CPL next Wed, for example.

I disagree. I would guess that in most cases, users don't want to
manually reprogram their CPL behavior each time they change their
calendar. 

In addition, I want the ability to say "I'm in a lecture TuTh 2.40-4.20,
for N weeks and thus don't bother calling me during that time". I have
this in my calendar - why should I re-enter this manually into a CPL
interface?

(Indeed, I recently came across one commercial product, Swyx, that
claims to do this integration of Outlook and call filtering, very much
in the same way apparently.)

Also, I've done a translation of the Sun calendar manager rules (which
are fairly similar to the iCal features, from what I can tell) and it
wasn't that hard, as long as you had a system routine that could convert
various time notations into one another. You basically end up running a
loop computing matching days/times and subtract the exceptions.