Theory about DFA's and f?lex start states

I've been writing a scanner generator which has the same notion of
exclusive start states as seen in GNU flex.


However, the implementation I've been working on uses stack
instructions to maintain the current start_state. Thus, rather than
lex rules which explicitly say "BEGIN(COMMENT)", it might say
"PUSH(COMMENT)" and "POP()". I've been describing the automata that
can be used to recognize such grammars as "Deterministic Pushdown
Finite Automata" (DPDFA's).


My reason for posting however is to ask if people know of any research
or investigation into the types of languages that are described by
flex-like regular grammars (ie the combination of DFA's and STATES). Is
there theory for this stuff or are multistate lexers just a pragmatic
incremental improvement on DFA research?


Thanks,
Paul

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