Festival is distributed with rxp an XML parser developed
by Richard Tobin of the Language Technology Group, University of
Edinburgh. Sable is set up as an XML text mode so no
further requirements or external programs are required to synthesize
from Sable marked up text (unlike previous releases). Note that rxp
is not a full validation parser and hence doesn't check some aspects
of the file (tags within tags).
Festival still supports SGML based markup but in such cases requires an external SGML normalizing parser. We have tested nsgmls-1.0 which is available as part of the SGML tools set sp-1.1.tar.gz which is available from http://www.jclark.com/sp/index.html. This seems portable between many platforms.