VGM implementation by using regular expression derivation algorithm.

This implementation bridges a gap between neutral grammar model (com.sun.msv.grammar) and Verifier grammar model (com.sun.msv.verifier).

## Performance Analysis

This bridge is tuned for client-side use, where MSV is repeatedly invoked from command line. Particularly,

1. No preprocessing of grammar is necessary. Abstract grammar model can be directly used. This results in faster schema loading, at the expense of slower validation.
2. Extensive error recovery and detailed error diagnosis is provided.

Also, this bridge covers full expressiveness of RELAX and TREX.

## Algorithm

Those who are interested in the algorithm of this package may want to see the following resources.

regexp.tar.gz
  regular expression matching algorithm by Mark Hopkins.
How to validate XML
  A brief introduction of the above algorithm by Joe English
TREX implementation
  This implementation by James Clark employs the algorithm of Mark Hopkins.