We investigate the inferrability of E-pattern languages (also known as extended
or erasing pattern languages) from positive data in Gold’s learning model. As the
main result, our analysis yields a negative outcome for the full class of E-pattern
languages – and even for the subclass of terminal-free E-pattern languages – if the
corresponding terminal alphabet consists of exactly two distinct letters. Furthermore,
we present a positive result for a manifest subclass of terminal-free E-pattern
languages. We point out that the considered problems are closely related to fundamental
questions concerning the nondeterminism of E-pattern languages