The goal of the TEI Overlapping Markup SIG is to bring together users of the TEI who are acutely interested in issues of multiple hierarchies and in particular handling those in XML. It will do this by:
XCONCUR is an experimental markup language with the major goal to provide a convenient method to express concurrent hierarchies in an XML-like fashion. XCONCUR-CL is a validation component in XCONCUR and allows cross-layer validation.