[CAP] update segments

[Mick Jagger]

Hi,
	In working(slowly) on an implementation guide for CAP to be added to the CAP cookbook, there are some cases that I wanted to get this group's opinion on.  What are the best methods to handle update and cancel messages that add or remove a data segment like area or resource?
	For example, an alert is issued for area A.  Then an update is issued for the same alert that now includes area B and C.  Should a seperate alert message go out for B and C, or just an update to the original that includes A, B, C?  Now, how about a cancel message for just area B.  Should it be an actual cancel message for B, or an update for just area B with the description saying that its cancelled for that area, or an update to A, B, C saying that B is not longer covered and future messages drop the B area?  
	I wanted to get a sense of the actual intended method of handling these situations and the methods any current implementations have chosen.  Thanks,

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