Re: [calsify] JSCalendar: fractional seconds

[Ken Murchison <[e-mail]>]

On 6/10/19 12:16 PM, Ken Murchison wrote:
>
> Would it make sense to change the parameter name to SUBSECOND as its a 
> known term?
>
> This also would allow extending recurrence rules to have a matching 
> SUBSECONDLY frequency if needed.  As stated early in the thread, a 
> libical user wants to extend RRULE to do exactly this.
>
Hmm, but since INTERVAL is an integer, we would have to specify the 
scale for subseconds (milli, micro, pico, nano?)  Or we allow 
MILLISECONDLY, etc as frequencies.


> On 6/6/19 9:07 AM, Robert Stepanek wrote:
>> This is a draft specification, happy about any input:
>>
>> 2.1.  FRACSEC parameter
>>
>>    Parameter name:  FRACSEC
>>
>>    Purpose:  This parameter is used to define fractional seconds for
>>       time values and durations.  It is meant to preserve time precision
>>       on time values and duration with sub-second precision, without
>>       increasing the time value range within iCalendar.
>>
>>    Description:  This parameter MAY be specified on properties of type
>>       DATE-TIME or DURATION.  The integral part of the float value MUST
>>       be zero.  The value MUST NOT be negative. iCalendar
>>       implementations MAY ignore this parameter in date time arithmetic.
>>       Implementations MUST ignore presence of the FRACSEC parameter on
>>       RECURRENCE-ID properties when determining recurrence overrides.
>>       If present on a RECURRENCE-ID property, its value MUST match the
>>       FRACSEC parameter value on the DTSTART property.
>>
>>    Format Definition:
>>
>>    This parameter is defined by the following notation:
>>
>>                                        fracsec-param = float
>>
>>    Example:  DTSTART;FRACSEC=0..03:20190605T133015
>>
>>
>>
>> On Thu, Jun 6, 2019, at 1:56 PM, Ken Murchison wrote:
>>> As a related topic, a libical user/developer submitted a PR to add 
>>> millisecond precision to time values. I haven’t committed it because 
>>> it simply changes the DATETIME values which certainly isn’t 
>>> backwards compatible. I suggested a new VALUE type but even that 
>>> isn’t compatible with unaware clients.
>>>
>>> Regardless, there does appear to be *some* desire to have fractional 
>>> seconds support in iCalendar.
>>>
>>> --
>>> Kenneth Murchison
>>> Cyrus Development Team
>>> FastMail US LLC
>>> [e-mail]
>>>
>>>
>>>
>>> On Thu, Jun 6, 2019, at 8:04 AM, Marten Gajda wrote:
>>>>
>>>> Is this parameter is meant to preserve the fractional seconds for 
>>>> round-trips or are iCalendar clients encouraged to use the value?
>>>>
>>>> I mean, would a client that's aware of X-FRACSEC have to match 
>>>> RECURRENCE-IDs ,RDATES and EXDATES taking the fractional seconds 
>>>> into account?
>>>>
>>>> I think we should advise against that and make clear that this is 
>>>> not meant to increase the precision of times in iCalendar, but 
>>>> merely to preserve it.
>>>>
>>>> Btw, how do we cope with unaware clients doing partial updates? 
>>>> I.e. a client which is not aware of X-FRACSEC adds a new 
>>>> recurrence-override (not adding X-FRACSEC to RECURRENCE-ID). When 
>>>> being converted back to JSCalendar, this would result in an 
>>>> additional instance instead of an override.
>>>>
>>>> Marten
>>>>
>>>> Am 06.06.19 um 13:49 schrieb Robert Stepanek:
>>>>> It just occurred to me that the current JSCalendar RFC draft 
>>>>> ambiguously defines if fractional seconds are allowed in the 
>>>>> LocalDate time type.
>>>>>
>>>>> To be clear: we intend to allow fractional seconds in the start 
>>>>> property (and any other LocalDate property). The next version of 
>>>>> the RFC draft will define this more clearly.
>>>>>
>>>>> Unfortunately, fractional second date-times and durations can not 
>>>>> be round-tripped out of the box with iCalendar. We will define an 
>>>>> iCalendar extension parameter in the informational guide for 
>>>>> mapping iCalendar and JSCalendar 
>>>>> (draft-ietf-calext-jscalendar-icalendar):
>>>>>
>>>>>   * X-FRACSEC of value type INTEGER
>>>>>   * This parameter MAY be set on iCalendar properties of type
>>>>>     DATE-TIME or DURATION. It MUST NOT be set more than once per
>>>>>     property.
>>>>>   * The value of this parameter defines the fractional seconds of
>>>>>     the DATE-TIME or DURATION type.
>>>>>   * This will allow iCalendar implementations  not being aware of
>>>>>     this extension parameter to display the time value "good
>>>>>     enough" with second precision.
>>>>>
>>>>>
>>>>> Please let me know if you prefer another approach.
>>>>>
>>>>> Cheers,
>>>>> Robert
>>>>>
>>>>> _______________________________________________
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>>>>>
>>>> -- 
>>>> Marten Gajda
>>>> CEO
>>>>
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>>>> Schandauer Straße 34
>>>> 01309 Dresden
>>>> GERMANY
>>>>
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>>>>
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> -- 
> Ken Murchison
> Cyrus Development Team
> FastMail US LLC
>
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-- 
Ken Murchison
Cyrus Development Team
FastMail US LLC