Clarification of Demand Charge DurationType elements

[Anne Hendry <ahendry@pacbell.net>]

Regarding Demand Charge Elements:

The four elements/attributes below, are part of "Demand Charge".  They are all of type emix:DurationType.  I can understand the reason for 3 of these, but not the fourth.  Here is my current understanding:

Measurement Interval:
    The time period over which average peak demand is measured (e.g., 15 minutes, 30 minutes, ..)
Collection Interval:
    Collection of Measurement Intervals.  Demand Charge is based on single highest average peak demand taken from all the Measurement Intervals contained in the Collection Interval.
Collection Period:
   Is this the billing period?
Charge Duration:
   Or is this the billing period?

PRD 02

Demand Charge Element	Definition
Measurement Interval	Granularity or Power Use readings. For example the demand charge may be incurred of the Power is above the floor for 5 minutes.
Collection Interval	Period during which power usage is summed for comparison to Demand Floor.
Collection Period	Period during which the Demand Charge applies
Charge Duration	Period during which Demand Charges will be applied after incurred.