# Saxon extensions to XML Schema 1.1

The Working Draft XSD 1.1 specification allows implementations to define their own primitive types and facets.

At present Saxon provides one additional facet, `saxon:preprocess`

Saxon extensions to the XML Schema Language are implemented in the Saxon namespace `http://saxon.sf.net/`:

- Messages associated with assertions and other facets

- The saxon:preprocess facet

- Saxon extensions to XSD uniqueness and referential constraints

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