XML Schema coding requirements

DITA coding practices for XML Schema rely on the XSD redefine facility in order to implement specializations or constraints. However, limitations in the redefine facility can present problems for some DITA modules implemented in XML Schema.

XSD-based document-type shells are organized into sections; each section contains a specific type of declaration.

Structural and domain vocabulary modules have the same XSD coding requirements for element type declarations.

An XSD structural module declares a top-level map or topic type. It is implemented as a pair of XSD documents, one that defines groups used to integrate and override the type and one that defines the element types specific to the type.

An attribute domain vocabulary module declares one new attribute specialized from either the @props or @base attribute.

A structural constraint module defines the constraints for a map or topic element type. A domain constraint module defines the constraints for an element or attribute domain.