A new approach for combining multiple vocabularies is presented. Rather than creating a monolithic schema by combining the schemas for several markup vocabularies, this approach decomposes a document into pieces and then validates each piece against one of these schemas. One advantage of this approach is that it allows the combination of multiple schema languages such as W3C XML Schema and and RELAX NG. This approach is expected to result in an ISO standard, namely ISO/IEC JTC1 DSDL Part 4 Selection of Validation Candidates.