>> Fourth, I still just don't get it. What's so hard about PIs? > >One thing that's hard is the rules about how REs adjacent to PIs are >handled. David Durand and I independently came up with a good way of dealing with such things (he had the idea before me, as Setev later let me know): define RE and RS such that they'll never occur in an XML document. That alone will simplify parsers a great deal.