SSML 1.0 Schema (20040615)
Copyright 1998-2004 W3C (MIT, ERCIM, Keio),
All Rights Reserved. Permission to use, copy, modify and
distribute the SSML schema and its accompanying documentation
for any purpose and without fee is hereby granted in
perpetuity, provided that the above copyright notice and this
paragraph appear in all copies. The copyright holders make no
representation about the suitability of the schema for any purpose.
It is provided "as is" without expressed or implied warranty.
restriction: version and attributes on speak mandatory
restriction: src attribute on audio is mandatory
restriction: name attribute on mark is mandatory