METHOD:COUNTER Validator.
Component/Property Presence
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METHOD 1 MUST be "COUNTER"
VEVENT 1
DTSTAMP 1
DTSTART 1
ORGANIZER 1 MUST be the "Organizer" of the original
event
SEQUENCE 1 MUST be present if value is greater than 0,
MAY be present if 0
SUMMARY 1 Can be null
UID 1 MUST be the UID associated with the REQUEST
being countered
ATTACH 0+
ATTENDEE 0+ Can also be used to propose other
"Attendees"
CATEGORIES 0 or 1 This property may contain a list of values
CLASS 0 or 1
COMMENT 0 or 1
CONTACT 0+
CREATED 0 or 1
DESCRIPTION 0 or 1
DTEND 0 or 1 if present DURATION MUST NOT be present
DURATION 0 or 1 if present DTEND MUST NOT be present
EXDATE 0+
EXRULE 0+
GEO 0 or 1
LAST-MODIFIED 0 or 1
LOCATION 0 or 1
PRIORITY 0 or 1
RDATE 0+
RECURRENCE-ID 0 or 1 MUST only if referring to an instance of a
recurring calendar component. Otherwise it
MUST NOT be present.
RELATED-TO 0+
REQUEST-STATUS 0+
RESOURCES 0 or 1 This property may contain a list of values
RRULE 0+
STATUS 0 or 1 Value must be one of CONFIRMED/TENATIVE/
CANCELLED
TRANSP 0 or 1
URL 0 or 1
X-PROPERTY 0+
VALARM 0+
VTIMEZONE 0+ MUST be present if any date/time refers to
a timezone
X-COMPONENT 0+
VTODO 0
VJOURNAL 0
VFREEBUSY 0