I've been going through the spec recently, and I have a few questions about DFDL regular expressions. Rather than put them into one long email, I'll break them up into separate emails. First question: What level of conformance to Unicode Technical Standard #18 UNICODE REGULAR EXPRESSIONS do DFDL regular expressions claim? For example, * XML Schema regular expressions are "targeted at support of 'Level 1' features" (http://www.w3.org/TR/xmlschema-2/#dt-ccesN) * Java 1.4 regular expressions "implement its second level of support" (http://docs.oracle.com/javase/1.4.2/docs/api/java/util/regex/Pattern.html) * Perl 5.18 seems to implement most of Level 1 (http://perldoc.perl.org/perlunicode.html#Unicode-Regular-Expression-Support-...) I think the conformance level should be specified in the DFDL spec so that it is clear to schema designers what a regular expression would really match against. Details like case conversion and canonical equivalence make a difference when matching against a Unicode string. Thanks in advance, -- Jonathan W. Cranford <jcranford@mitre.org> Senior Information Systems Engineer The MITRE Corporation (http://www.mitre.org)