99% is a great result! Well done Michael Kay. I am continually impressed by SAXON. Organizations that use it should assertively consider buying licenses, in order to let Dr Kay keep up the good work. Of course, large test suites have many repeats, so probably 99% of tests passing is not the same as 99% of features covered. Of course, technical specs are only really aimed at the handful of implementers and writers to understand; they just aren't end-user documents. And the XSD Structures spec has many virtues as well as its obvious shortcomings. To a certain extent, end-users never need to check the specification if either the technology is straight-forward enough (guessable) or if the user documentation and diagnostics are clear enough. So the question with XSD is not only "Can the spec be made clearer?" but also "Can comprehensible user documentation be made?" and "Can end-user comprehensible diagnostics be made?" Both these are areas of sheer man-hours, which is where buying SAXON licenses can directly help: if you organization is using XSD as a mission-critical part, you really should treat licensing as a basic part of risk-management.