XML is based on Unicode, and therefore XML documents may use the full Unicode character repertoire. However, XML-based applications often use XML interfaces to legacy software which in many cases is not capable of dealing with the full Unicode character repertoire. We therefore propose a schema language for XML which is capable of limiting the character repertoire of XML documents. This schema language, called Character Repertoire Validation for XML (CRVX), has features to permit or disallow character repertoire subsets from certain parts of an XML document, for example only for element and attribute names. CRVX uses information from the Unicode Character Database (UCD) to make character repertoire specification as easy as possible. CRVX is not intended to be the only schema language in an XML application scenario, but it provides useful additional schema-based validation to protect applications from unsupported characters. XML applications typically combine dierent