The W3C XML Schema Working Group has released an initial working draft for XML Schema: Component Designators. The specification defines a system for designating XML Schema components. The document addresses a range of problematic issues in the use of a QName to designate schema components as defined in the W3C XML Schema Recommendation. "The schema-as-a-whole schema component may represent the amalgamation of several distinct schema documents, or none at all. It may be associated with any number of target namespaces, including none at all. It may have been obtained for a particular schema assessment episode by deferencing URIs given in schemaLocation attributes, or by an association with the target namespace or by some other application-specific means. In short, there are substantial technical challenges to defining a reliable designator for the schema-as-a-whole, particularly if that designator is expected to serve as a starting point for the other components encompassed by that schema. The editors propose to divide the problem of constructing schema component designators into two parts: defining a designator for an assembled schema, and defining a designator for a schema component, understood relative to a designated schema."

Bibliographic information: XML Schema: Component Designators. W3C Working Draft 09-January-2003. Edited by Mary Holstege (W3C Invited Expert) and Asir S. Vedamuthu (webMethods). First public working draft. Version URL: http://www.w3.org/TR/2003/WD-xmlschema-ref-20030109/. Latest version URL: http://www.w3.org/TR/xmlschema-ref/.

XML Schema components specified by the XML Schema Recommendation Part 1 and Part 2: "Part 1 of the W3C XML Schema recommendation defines these schema components; section 2.2 lays out the inventory of schema components into three classes: [1] Primary components: simple and complex type definitions, attribute declarations, and element declarations; [2] Secondary components: attribute and model group definitions, identity-constraint definitions, and notation declarations; [3] 'Helper' components: annotations, model groups, particles, wildcards, and attribute uses. In addition there is a master schema component, the schema component representing the schema as a whole. Finally, there are schema components for the facets defined in Part 2 of the W3C XML Schema recommendation: [A] Fundamental Facets: ordered, bounded, cardinality, numeric; [B] Constraining Facets: whiteSpace, minInclusive, maxInclusive, minExclusive, maxExclusive, totalDigits, fractionDigits, length, minLength, maxLength, pattern, enumeration."