[developers] type addenda and :< in TDL

[Rebecca Dridan]

Hi all,

Recently I have been playing with type addenda (using :+) to make some 
systematic changes to LE types (so far in ERG only).  I've run in to a 
few cases where the original type was defined with :< rather than :=, 
and hence won't allow modification.  This seems to be by design, since 
the distinction is built in to both LKB and PET, but I'm not sure if it 
is still intended to mean such.  My initial queries to Those Who Know 
said that := and :< are equivalent, and :< is a historical artifact.

Is there anyone currently using :< to mean 'don't allow features on this 
type' (or to mean anything else)? Is there any reason to keep this 
distinction?

Rebecca