What is a "tagged DFA"?

Question

I came across a regular expression library http://laurikari.net/tre/ and also http://hackage.haskell.org/package/regex-tdfa , but I could not find anything about this "tagged DFA" approach that they are using: neither on the pages of these libraries, nor in google (incl.scholar).

Anyone know what it is about?

Answer 1

Here is a paper:

NFAs with Tagged Transitions, their Conversion to Deterministic Automata and Application to Regular Expressions (2000) [PDF], written by Ville Laurikari.