Specialization rules for element types
There are certain rules that apply to element type specializations.
- Characteristics
-
A specialized element type has the following characteristics:
- A properly-formed
@class
attribute that specifies the specialization hierarchy of the element - A content model that is the same or less inclusive than that of the element from which it was specialized
- A set of attributes that are the same or a subset of those
of the element from which it was specialized,
except for specializations of
@base
or@props
- Values or value ranges of attributes that are the same or a subset of those of the element from which it was specialized
- A properly-formed
- Namespaces
-
DITA elements are never in a namespace. Only the
@DITAArchVersion
attribute is in a DITA-defined namespace. All other attributes, except for those defined by the XML standard, are in no namespace.This limitation is imposed by the details of the
@class
attribute syntax, which makes it impractical to have namespace-qualified names for either vocabulary modules or individual element types or attributes. Elements included as descendants of the DITA<foreign>
element type can be in any namespace.