XML Schema coding requirements

In this section:

1. XML Schema: Overview and limitations of 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.
2. XML Schema: Coding requirements for document-type shells
   XSD-based document-type shells are organized into sections; each section contains a specific type of declaration.
3. XML Schema: Coding requirements for element type declarations
   Structural and domain vocabulary modules have the same XSD coding requirements for element type declarations.
4. XML Schema: Coding requirements for structural modules
   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.
5. XML Schema: Coding requirements for attribute domain modules
   An attribute domain vocabulary module declares one new attribute specialized from either the @props or @base attribute.
6. XML Schema: Coding requirements for constraint modules
   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.