This is an archived snapshot of W3C's public bugzilla bug tracker, decommissioned in April 2019. Please see the home page for more details.
The validity of this expression hinges on the rules for use of "-" within a character class expression. The rules for this have a tortuous history and there are still bugs open against the XML Schema spec (see bug #1889) Currently the grammar rule [17] charRange ::= seRange | XmlCharIncDash states that hyphen is permitted in the context used in this example. Below this, the text (a) incorrectly states that the grammar is ambiguous, (b) in bullet 1 says that hyphen is not a valid character range (which flatly contradicts the grammar), and (c) in bullet 3 says that hyphen is a valid character range if it appears and the beginning or end of a positive character group (without saying what it means: on one interpretation this hyphen is at the end of a positive character group; it just doesn't happen to be the longest-possible positive character group). So the schema spec here is a mess and is essentially untestable until they sort this out.
This test is disabled now.