Re: The Goals of XML at 25, and the one thing that XML now needs

XML Features Not Supported

• 1. DTD external or internal subsets. Note that external subsets are optional in the XML Recommendation, but internal subsets are required [21]. In this respect XML Screamer is non-conforming.
• 2. Support for encodings other than UTF-8 or UTF-16. Our architecture is in principle capable of supporting other encodings, but because our parsers are hand crafted to optimize for the characteristics of particular encodings, the work involved is significant.
• 3. Very large instance documents, i.e. those too large to fit in a contiguous memory buffer.

XML Schema Features Not Supported

• 4. Facets on simple types (these are accepted but not checked; among the facets not checked is the pattern facet.) [Note 5]
• 5. Non-deterministic content models (such as certain models with nested numeric occurrence constraints.) [Note 6]
• 6. Identity constraints (accepted but not checked)
• 7. Validity checking of types other than anySimpleType, date, integer, decimal, nonnegativeInteger, boolean, positiveInteger,negativeInteger, nonpositiveInteger, and string (all types are accepted, but validation of lexical forms and conversion to binary is available only for the listed types.)