Compatibility-Rule Attributes

This specification describes the manner by which compatibility rules can be associated with any XML element, including Markup Compatibility elements. Compatibility rules are associated with an element by means of compatibility-rule attributes. These attributes control how markup consumers, including markup editors, shall react to elements or attributes from non-understood namespaces.

The principal compatibility-rule attribute is the @Ignorable attribute. By default, markup consumers should treat the presence of any element or attribute from a non-understood namespace as an error condition. However, elements and attributes from a non-understood namespace identified in an @Ignorable attribute shall be ignored without error.

Compatibility-rule attributes shall affect the element to which they are attached, including the element’s other attributes and contents. The order in which compatibility-rule attributes occur on an element shall not affect the application of those rules to that element, its attributes, or its contents.