Re: How is ambiguity defined?

> On 6,Jan2022, at 2:07 PM, Steven Pemberton <steven.pemberton@cwi.nl> wrote:
> 
> 
> > But sentential forms are sequences of terminal and nonterminal
> > symbols. The expression ‘a’*; ‘b’* is not a sentential form and
> > cannot appear as a step in a derivation, as that term is normally
> > defined. 
> 
> A nice try, but if I were to channel Chomsky, he would say that 
> 
>    s: a*; b*.
> 
> is a rewriting of
> 
>   s -> a*
>   s -> b*
> 
> which have two derivations for 𝜀

Sorry, I don’t see two derivations here.

It’s a simple grammar, and a very short input.  Can you exhibit the
two derivations you have in mind?

The reference to Chomsky sounds hopeful, but in what I have read of
his work, he does not consider grammars with rules in the form s -> a*
and s -> b*.  If we use Chomsky’s notion of derivation, I believe the
number of derivations we have is zero, not two.

Michael

Received on Thursday, 6 January 2022 23:11:42 UTC