3.7 Specialization elements
Several DITA elements exist either for architectural reasons or for support of
specialized markup yet to be designed. Although there is little need to use these elements
unless you are directed to, some of them, such as
<state>, can be
used if your content makes use of these semantic distinctions. For example, a discussion of
signals on a gate of an integrated logic circuit might use the
<state> element to represent either on or off conditions of that
<boolean> element was deprecated in DITA version 1.1. It was originally intended to express one of two opposite values, such as yes / no or on / off.
<data> element represents a property within a DITA topic or map. While the
<data> element can be used directly to capture properties, it is particularly useful as a basis for specialization. Default processing should treat the content as an unknown kind of metadata and ignore it for rendering, but custom processing
might match the
@name attribute or specialized element and use the element for automated manipulation or to format data associated with the body flow. For example, a specialized
might be used to format properties as sidebars or other adornments or to harvest properties for automated processing.
<data-about> element identifies the subject of a property when the subject isn't associated with the context in which the property is specified. The property itself is expressed by the
<data> element. The
<data-about> element handles exception cases where a property must be expressed somewhere other than inside the actual subject of the property. The
<data-about> element is particularly useful as a basis for specialization in combination with the
<foreign> element allows the introduction of non-DITA content, for example, MathML, SVG, or Rich Text Format (RTF). The
<foreign> element or a specialization
can contain more than one type of non-DITA content or a mix of DITA and non-DITA content. Specialization of the
<foreign> element generally is implemented as a domain, but architects looking for more control over the content
can implement foreign vocabularies as structural specializations.
<index-base> element allows indexing extensions to be added by specializing this element.
<itemgroup> element can be used to sub-divide or organize elements that occur inside a list item, definition, or parameter definition.
<no-topic-nesting> element is a placeholder in the DITA architecture. It is not actually used by the default DITA document types; it is for use only when creating a validly customized document type where the information designer wants to eliminate the ability to nest topics. Not intended for use by authors, and has no associated output processing.
<state> element specifies a name/value pair whenever it is necessary to represent a named state that has a variable value. The element is primarily intended for use in specializations to represent specific states (like logic circuit states, chemical reaction states, airplane instrumentation states, and so forth).
<unknown> element is an open extension that allows information architects to incorporate xml fragments that do not necessarily fit into an existing DITA use case. Processors should ignore this element unless otherwise instructed.