Calendar

A calendar represents a numeric value that is varying over time.

Calendars can be linked to multiple entities: a maximum capacity limit of a resource, a minimum capacity usage of a resource, a minimum or maximum inventory limit of a buffer, etc…

A calendar has multiple buckets to define the values over time. To determine the calendar value at a certain date the calendar will evaluate each of the buckets and combine the results in the following way:

  • A bucket is only valid from its “start” date (inclusive) till its “end” date (exclusive).
    Outside of this date range a bucket is never selected.
  • If multiple bucket are effective on a date, the one with the lowest “priority” value is taken.
    In case buckets have the same priority, the value of the bucket with the latest start date is selected.
  • In case no bucket is effective on a certain date, the calendar will return the “default” value.

Fields

Field Type Description
name non-empty string Name of the calendar. This is the key field and a required attribute.
default double The default value of the calendar when no bucket is effective.
action A/C/AC/R
Type of action to be executed:
A: Add an new entity, and report an error if the entity already exists.
C: Change an existing entity, and report an error if the entity doesn’t exist yet.
AC: Change an entity or create a new one if it doesn’t exist yet. This is the default.
R: Remove an entity, and report an error if the entity doesn’t exist.

Methods

Method Description
setValue([start date], [end date],[value]) Creates or updates calendar buckets to reflect the specified value in the given date range.
buckets() Returns an iterator over the calendar buckets.
events([start date], [direction])

Returns an iterator over the calendar events starting from the (optional) start date, either backward or forward in time. These are the dates at which the calendar value is changing.

Each event is a tuple with 2 fields:

  • date: date of the event.
  • value: value that becomes effective at the time of the event.

Calendar bucket

Field Type Description
id integer
Unique identifier within the calendar of the bucket.
When left unspecified in the input data it is automatically created.
start dateTime
Start date of the validity of this bucket.
When left unspecified, the entry is effective from the infinite past.
end dateTime
End date of the validity of this bucket.
When left unspecified, the entry is effective indefinitely in the future.
priority integer
Priority of this bucket when multiple buckets are effective for the same date.
Lower values indicate higher priority.
days integer between 0 and 127
Bit pattern representing the days on which the calendar bucket is valid:
Bit 0 = 1 = Sunday
Bit 1 = 2 = Monday
Bit 2 = 4 = Tuesday
Bit 3 = 8 = Wednesday
Bit 4 = 16 = Thursday
Bit 5 = 32 = Friday
Bit 6 = 64 = Saturday
The default value is 127, ie valid on every day of the week.
starttime duration
Time when this entry becomes effective on valid days in the valid date horizon.
The default value is PT0S, ie midnight.
endtime duration
Time when this entry becomes ineffective on valid days in the valid date horizon.
The default value is PT23H59M59S, ie right before midnight of the next day.
value double The actual time-varying value.

Example XML structures

Adding or changing a calendar and its buckets

<plan>
  <calendars>
    <calendar name="cal">
      <default>5</default>
      <buckets>
        <bucket start="2007-01-01T00:00:00" value="10" priority="1"/>
        <!-- This entry overrides the first one during February. -->
        <bucket start="2007-02-01T00:00:00" end="2007-03-01T00:00:00" value="20" priority="0"/>
      </buckets>
    </calendar >
  </calendars>
</plan>

Removing a calendar

<plan>
   <calendars>
      <calendar name="cal" action="R"/>
   </calendars>
</plan>

Example Python code

Adding or changing a calendar and its buckets

cal = frepple.calendar_double(name="cal", default=5)

Removing a calendar

frepple.calendar(name="cal", action="R")

Iterating over all buckets of a calendar

for b in frepple.calendar(name="cal").buckets():
  print b.name, b.value

Iterating over all events of a calendar, going forward in time from a certain date

start = datetime.datetime(2009,1,1)
for date, value in frepple.calendar(name="cal").events(start, True):
  print date, value