Xml Validation Interoperability Framework (xvif) is a proposal to embed pipe definitions in grammar based schema languages such as Relax NG (and probably W3C XML Schema). The current implementation is built on a partial implementation of Relax NG, supporting the features needed to provide a representative proof of concept. It is available both as Python source code and as an online demonstration. Although there is no endorsement of any kind by the DSDL ISO initiative (http://dsdl.org), one of the goals of this prototype is to gather feedback which may be used (or not) by "DSDL Part 1 - Interoperability Framework".