RELAX NG validation is supported natively in some editing environments, such as <oXygen/> (see Figure 3-1), XMLmind, and Emacs (with nxml-mode). <oXygen/> and XMLmind also support Schematron validation. There are also several standalone validators—for example, Jing and Sun’s Multi-Schema Validator (MSV).

If your documents make use of several namespaces (e.g., SVG and MathML embedded in DocBook), tools that support NVDL, Namespace-based Validation Dispatching Language [NVDL], can greatly simplify complex validation scenarios.

Figure 3-1. <oXygen/> XML Editor validation