528: Language is confusing

Rewote the introduction of the use of iCalendar as follows: 4.1 WS-Calendar in Energy Interop WS-Calendar defines how to use the semantics of the enterprise calendar communications standard iCalendar within service communications. WS-Calendar allows for ways to express a related group of time intervals as a sequence. It additionally allows for a way to abstract certain information of related intervals to avoid repetition of such information in every interval of the sequence. This abstraction is called a WS-Calendar gluon, and it can be related to a group of intervals in a sequence to represent the same information present in intervals, but applicable to all intervals in a sequence. Gluons can represent interval information such as "start time" and "duration" that would stay constant over time inside all the intervals in the sequence. Energy Interop uses EMIX to exchange descriptions of energy resources and products. WS-Calendar is also used directly within Energy Interoperation, to specify contracts such as availability and option call windows. For example, generation reserve may make themselves available only on summer afternoons on weekdays. Some tariffs may specify that suppliers may call for performance on Demand Response events only during a fixed schedule which may span times of day over several months. While these schedules can be difficult to communicate unambiguously, they are common in iCalendar; it is a common to schedule a meeting for Mondays and Wednesdays for the next two months. Because WS-Calendar is derived from iCalendar, it is able to express this availability.. WS-Calendar gluons associate with intervals in a sequence and share information with them. Gluons can control the start time and duration of intervals in a sequence. Gluons can contain the same artifacts as do intervals. A complex artifact may be shared between Gluon and each Interval in a sequence, so that invariant information is expressed only once, in the Gluon, and the information that changes over time, perhaps price or quantity, is the only part of the Artifact in each interval. Practitioners should read [WS-Calendar] to fully the expressiveness of that specification.