Separator character needs to be determined from JS.
In the case of Ajax within a composite component, all component IDs are
typically dyamically created, so it will be common for IDs to be determined by
substringing, using the clientID separator character.
If JSF is ever to change the separator character in the future, there must be a
Alternately, the EG could just decide that the separator character will always
be ":" going forward.