Subject: RE: BYDAY and YEARLY

From: [email-masked]
Date: Fri, 18 Jul 2003 02:00:09 -0400

Dan, I asked Frank to post his comments on the list.  I know he's been out
of the country.  I'll try to nudge him.  He chatted with the other author
so they could formulate a reply for the list.
___________________
Patricia Egen Consulting
www.egenconsulting.com
423-875-2652

                      "Dan Hickman"                                                                                                     
                      <dhickman@rockinso        To:       <[email-masked]>                                                   
                      ftware.com>               cc:       <[email-masked]>, <[email-masked]>, "Jonathan Lennox"     
                                                 <[email-masked]>, <[email-masked]>                           
                      07/16/2003 10:32          Subject:  RE: BYDAY and YEARLY                                                          
                      PM                                                                                                                

Any  luck talking to the original authors.  I think we need to make a
ruling on  this and get on down the road.

At  this point, I feel it makes the most sense to conclude that
"RRULE:FREQ=YEARLY;BYDAY=-1SU;BYMONTH=10" means "The last Sunday in
October".

Regards,
Dan  Hickman
Rockin' Software
[email-masked]
http://www.rockinsoftware.com

-----Original Message-----
From:  [email-masked]
[mailto:[email-masked]]On Behalf Of
[email-masked]
Sent: Tuesday, July 08, 2003 9:49  PM
To: Dan Hickman
Cc: [email-masked];  [email-masked]; Jonathan Lennox;
[email-masked]
Subject: RE: BYDAY and  YEARLY

We are in dialog  with the original authors - maybe we can try to get some
sort of ruling on  what they think this should be.  And if it's wrong, we
need to get it  fixed.  We need to make some adjustments to the RFC's
anyway because of  findings from interop testing.
___________________
Patricia Egen  Consulting
www.egenconsulting.com
423-875-2652

      "Dan Hickman"                                                       
      <dhickman@rockinsoftwa                To:                           
      re.com>                       <[email-masked]>,        
      Sent by:                      "Jonathan Lennox"                     
      owner-ietf-calendar@ma        <[email-masked]>              
      il.imc.org                            cc:                           
                                    <[email-masked]>               
      07/08/2003 20:37                      Subject:         RE: BYDAY    
                                    and  YEARLY                           

The one  thing that is obvious given the repeated conversations  on this
topic is  that the specification of BYDAY on YEARLY is ambiguous in the
RFC. I see  both sides asvalid  interpretations. I suppose the real
question is what  was the original intention  of the author(s)?

Given the following:
1.  umerous VTIMEZONE  examples in the RFC use
"RRULE:FREQ=YEARLY;BYDAY=-1SU;BYMONTH=10" to mean   "The last Sunday in
October", making it a big statement to say that  these  are not valid.
2.There are a number of   implementations that already work this way now.
3.Rules like "The 5th Monday of the year but  only in February"  are
probably not that useful.

it appears there is  much less impact if we go ahead and consider
"FREQ=YEARLY;BYMONTH=2;BYDAY=5MO" to mean the "5th Monday in   February". I
suggest we accept this  interpretation.

Too bad I picked the wrong  interpretation to  implement :-|

Regards,
Dan  Hickman
Rockin' Software
[email-masked]
http://www.rockinsoftware.com
-----Original Message-----
From:   [email-masked]
[mailto:[email-masked]]On Behalf Of
[email-masked]
Sent:  Tuesday, July 08, 2003 2:07  PM
To:  Jonathan Lennox
Cc:   [email-masked]
Subject: Re: BYDAY  and  YEARLY

Jonathan wrote on  07/08/2003  11:35:11 AM:
> I agree  with this so far, but in your next step  (concluding that this
means
> "the last Sunday in October") you  make an  unwarranted leap.  The
definition
> of the integer parts of BYDAY  says, as you quoted  previously:
>
> >    Each BYDAY  value can also be preceded  by a positive (+n) or
negative
> >      (-n) integer. If present, this indicates the nth occurrence  of
the
> >    specific  day within the MONTHLY or YEARLY RRULE.
>
> Thus, since this is a  YEARLY RRULE, the phrase "Last Sunday"  means
"Last
> Sunday of the Year", not "Last Sunday of the Month."    The presence of a
> BYMONTH  rule doesn't affect this; by the spec,  the integer part of
BYDAY
> depends *only* on the   FREQ.

The assumption about  BYDAY  would be accurate without other BYxxx
modifiers present.  When I   read:

    If multiple BYxxx rule  parts are specified, then after evaluating  the
  specified FREQ and  INTERVAL  rule parts, the BYxxx rule parts are
   applied to the current  set of evaluated occurrences in the  following
  order:

I take the phrase "applied to the  current  set of evaluated occurrences"
to be that BYDAY works on the  modified  occurrences generated by applying
the BYMONTH first.  This  BYxxx modifier  scopes the instance set to the
month of October rather  than the entire year.

If BYMONTH were multivalued  (ie: BYMONTH=10,11,12) then the  occurrences
would be scoped to the months of  October thru December.   If no other
BYxxx rule parts were there then Id  say that the rule  would evaluate to
"The last Sunday in December" but because  other BYxxx  modfiiers were
involved this is not true.

On the top of page 45 in 2445 there is an example  of  this that is pretty
similar to Dans rule:

   Here is an example of evaluating  multiple BYxxx rule  parts.

     DTSTART;TZID=US-Eastern:19970105T083000
      RRULE:FREQ=YEARLY;INTERVAL=2;BYMONTH=1;BYDAY=SU;BYHOUR=8,9;
      BYMINUTE=30

  First, the "INTERVAL=2" would be  applied  to "FREQ=YEARLY" to arrive
  at "every  other year". Then,  "BYMONTH=1" would be applied to arrive
  at "every January, every  other year". Then,  "BYDAY=SU" would be
  applied to arrive  at "every  Sunday in January, every other year".
...

This  evaluates just like I did for the  BYDAY=-1SU;BYMONTH=10.  It
follows the same logic I used (or I should say  that my logic followed it
w/o actually seeing this @ first) by applying the  cited bits of  2445.

>                                                                   But
this  just
> means that the quoted  rule is  vacuous, and its recurrence defines the
empty
> set, except for  its DTSTART.

I do not  think so given that the  evaluation of the rule matches the way
that the  multiple BYxxx parts are  described to modify each other (and are
not applyed  in parallel) and  that the example in 2445 seems to confirm
this.

Bruce
===========================================================================
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---

From: [email-masked]
Date: Fri, 18 Jul 2003 14:09:43 -0400

Cool.  8-)
___________________
Patricia Egen Consulting
www.egenconsulting.com
423-875-2652

                      Doug Royer                                                                                                           
                      <[email-masked]>             To:       [email-masked]                                                         
                      Sent by:                     cc:                                                                                     
                      owner-ietf-calendar@m        Subject:  Re: BYDAY and YEARLY                                                          
                      ail.imc.org                                                                                                          

                      07/18/2003 01:58 PM                                                                                                  
                      Please respond to                                                                                                    
                      ietf-calendar                                                                                                        

[email-masked] wrote:
>
> Doug, we are not getting input off the list.  We're asking that their
> responses be put on the list - not off of it.  You should know by now
that
> I don't favor discussions off of the list - and never have.

Thank you. I really did know that and I do and have believed you felt
that way and have promoted that everything is on the list. It just
appeared to me as if for convenience and *not* for subversion that
it may had happened.

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