The XML Namespaces Recommendation allows an XML document to be composed of elements and attributes from multiple independent namespaces. Each of these namespaces may have its own schema; the schemas for different namespaces may be in different schema languages. The problem then arises of how the schemas can be composed in order to allow validation of the complete document. This document proposes the Namespace Routing Language (NRL) as a solution to this problem. NRL is an evolution of the author's earlier Modular Namespaces (MNS) language.