Who uses it?
Out of 291 packages, the only uses seem to be - Defining TEST-OP operations (greate majority) - In a few tests, it solves a wrong ordering of files - In two, it deactivates operations by using FEATURE (obscure way to do it)
The "paradigmatic" example of McClim cited here
http://common-lisp.net/project/asdf/asdf.html#Common-attributes-of-component... does not have a single occurrence of this word.
The question is thus, is it really needed?
Juanjo