Merging of cascading attributes
The @cascade attribute can be used to modify
the additive nature of attribute cascading,
although it does not turn off cascading altogether. The
attribute has two predefined values: merge and
nomerge.
- merge
- Indicates
that the metadata attributes cascade, and that the
values of the metadata attributes are additive. This is the
processing default for the
@cascadeattribute. - nomerge
- Indicates
that the metadata attributes cascade, but that they are
not additive for
<topicref>elements that specify a different value for a specific metadata attribute. If the cascading value for an attribute is already merged based on multiple ancestor elements, that merged value continues to cascade until a new value is encountered. That is, settingcascade="nomerge"does not undo merging that took place on ancestor elements.
If no value is set for the @cascade attribute and no value cascades from a
containing element, processors SHOULD assume a
default of merge.
Implementers MAY define their own custom, implementation-specific tokens
for the @cascade attribute. To avoid name conflicts between implementations
or with future additions to the standard, implementation-specific tokens SHOULD consist of a prefix that gives the name or an
abbreviation for the implementation followed by a colon followed by the token or method
name. For example, a processor might define the token "appToken:audience" in order to
specify cascading and merging behaviors for only the @audience
attribute.
The predefined values for the @cascade attribute MUST precede any implementation-specific tokens, for
example, cascade="merge appToken:audience".