map:aggregate can have a label, but doesn't match view from-position="first" like generators
each map:part can have a label
if at least one of the parts has a label matching the current view, only parts matching
this view are added. Otherwise, all parts are added.
For more info on aggregation and views, see the mail archive
here or
here.
author: Sylvain Wallez version: $Id: AggregateNode.java 433543 2006-08-22 06:22:54Z crossley $