W3C XML Schema Definition Language (XSDL)

Members of the W3C XML Schema Working Group have released a Last Call
Public Working Draft for the "W3C XML Schema Definition Language (XSDL)
1.1 Part 1: Structures" specification, updating the previous WD of
31-August-2006. The Last Call review period for this document extends
until 8-November-2007. Comments on this document should be made in W3C's
public installation of Bugzilla, specifying "XML Schema" as the product.
The "Structures" document specifies the XML Schema Definition Language,
which offers facilities for describing the structure and constraining
the contents of XML documents, including those which exploit the XML
Namespace facility. The schema language, which is itself represented in
an XML vocabulary and uses namespaces, substantially reconstructs and
considerably extends the capabilities found in XML document type
definitions (DTDs). This "Structures" specification depends on "XML
Schema Definition Language 1.1 Part 2: Datatypes." XSDL 1.1 retains all
the essential features of XSDL 1.0, but adds several new features to
support functionality requested by users, fixes some errors in XSDL 1.0,
and clarifies some wording. Some of the major revisions since the
previous draft include: (1) A mechanism for conditional type assignment
has been defined; this allows the 'governing type definition' to be
assigned by evaluating information in the instance document. (2) Element
declarations may now specify multiple substitution group heads. (3) A
default attribute group may now be specified at the schema-document
level; all complex types defined in the schema document will include
that attribute group unless they specify otherwise; this makes it easier
to specify that particular attributes are to be accepted by every complex
type in a schema. (4) Content models may now be defined as "open", which
means that elements other than those explicitly named will be accepted
during validation. Several styles and degrees of openness are possible;
they can be configured at the level of the schema document or of the
complex type definition. (5) Wildcards may now be defined which match
only elements not declared in the schema -- so-called "not-in-schema"
wildcards. (6) Complex types whose content models are all-groups may now
be extended. (7) The assertions facility defined in the previous working
draft has been revised; the changes may help minimize confusion between
the assertions defined here and the assert and report elements of
Schematron. (8) Elements may now have more than one attribute of type
'xs:ID'. (9) Various enhancements to the definition of the
'post-schema-validation infoset' (PSVI) have been made. (10) Some
aspects of the use of xsi:type have been clarified. (11) A
conditional-inclusion mechanism has been defined to allow XSDL 1.1
processors to cope more successfully with constructs defined in future
versions of this specification [and] so that the same schema document
can be usable with processors supporting different versions of XSDL.

See also XML Schema languages: CHECK HERE