Here is information about some of the tools mentioned in this book. If you are running Linux, you may be able to load some of these tools using a package manager like Synaptic, yum, or apt. Needless to say, this is not a comprehensive list; there are other capable tools available. However, these are a good starting place.
A variety of tools that support RELAX NG can be found at: http://relaxng.org/. These include:
Sun Multi-Schema XML Validator (from Sun Microsystems). MSV is an open source program that validates RELAX NG as well as other schema languages including W3C XML Schema.
An open source RELAX NG validator that supports both compact and XML syntax.
An open source program that is a companion to Jing, Trang converts between various XML schema languages. It supports both compact and XML syntax for RELAX NG, XML 1.0 DTDs, and W3C XML Schemas, though it only supports W3C XML Schemas for output.
This is an open source addon for emacs that supports syntax-directed editing using a RELAX NG compact mode schema. It validates as you type and will show you at any point what the valid set of elements, attributes, and attribute values is. It also supports automatic completion of partially typed elements, attributes, and attribute values.
Saxon is an XSLT processor. The basic processor ...