Kohsuke Kawaguchi announced the release of RelaxMeter, an MIT-licensed Java tool that demonstrates that an "unambiguous subset of RELAX NG can be easily defined".

While RELAX NG's ability to describe ambiguous structures is generally considered a feature rather than a bug, the developers who want their schemas to produce strictly determinate type structures have criticized RELAX NG's flexibility in this area.

Using RelaxMeter, developers can test RELAX NG schemas to find out how tolerant of ambiguity those schemas are.

"A schema judged as 'unambiguous' by this tool is guaranteed to yield only one type assignment, and the process of assigning types to XML documents can be done *independently* from RELAX NG validation process.... To be precise, this tool roughly checks if a grammar is in a class called 'single type'. For detailed discussion about "single typeness", wait for upcoming paper by MURATA Makoto et al."

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• XML and the IETF: Making the case for RELAX NG
• RELAX NG gets "feasible validation" support