C.4 Undeclared entities?

On 23 October 1996, the ERB will vote to decide the following
question.  A straw poll indicates the ERB is leaning to declaring
only lt, gt, and amp automatically and making references to
undeclared entities be a reportable error.

C.4 if XML makes DTDs optional and allows partial DTDs, what must or
may a parser do when it encounters references to undeclared entities
(9.4)?  Should XML declare any set of entities automatically?