inherent ambiguity

[stdvu]

how do one prove that the language is inherently ambigous? like for example in languages that use unions such as
L = L1 U L2, where
L1 = {a^m b^m c^n | m,n>0}
L2 = {a^m b^n c^n | m,n>0}

[JosAH]

how do one prove that the language is inherently ambigous? like for example in languages that use unions such as
L = L1 U L2, where
L1 = {a^m b^m c^n | m,n>0}
L2 = {a^m b^n c^n | m,n>0}

If the intersection of L1 and L2 isn't empty while L1 != L2 the union of both
languages L1 U L2 is ambiguous. Note that the problem L1 == L2? is an
undecidable problem. See the Post Correspondence Problem for a fundamental
proof.

kind regards,

Jos