Conformance for XDITA authoring applications

An application that supports XDITA authoring MUST:

• Constrain the set of available elements and attributes to those defined by this specification, with no or minimal configuration required.
• Generate valid LwDITA topics.
• Support authors in authoring valid XDITA maps, to define sets of LwDITA (XDITA, HDITA, or MDITA) topics.

An application that supports XDITA authoring MAY:

• Support authors, possibly in a graphical user interface, in setting the @props filtering attribute.
• Support authors, possibly in a graphical user interface, in inserting valid content references.
• Show or preview representations of XDITA topics with content references resolved and filtering applied.
• keyref? authoring support preview?