unionsynopsis — The syntax summary for a union-of-types definition.


unionsynopsis ::=


Common attributes and common linking attributes.

Additional attributes:

  • language
  • ordered (enumeration)
    • “0”
    • “1”
  • packageref

Additional Constraints

  • If this element is the root element, it must have a version attribute.


A unionsynopsis contains the syntax summary of a union (generally speaking, unions programming language sense).

This is one of the few places where DocBook attempts to model as well as describe. The content model of unionsynopsis was designed to capture a wide range of semantics.

Processing expectations

Formatted inline.


Common attributes and common linking attributes.

any attribute

Any attribute in any other explicit namespace


Identifies the language (i.e. programming language) of the content


Indicates how the value of a union is specified.

Enumerated values:

Value of enum is specified explicitly using enumvalue


Value of enum is inferred from its position


Identifies the package to which this synopsis (logically) belongs


These elements contain unionsynopsis: abstract, acknowledgements, annotation, answer, appendix, article, bibliodiv, bibliography, bibliolist, blockquote, callout, calloutlist, caption (db.caption), caution, chapter, colophon, constraintdef, cover, danger, dedication, entry, example, figure, footnote, glossary, glossdef, glossdiv, glosslist, important, index, indexdiv, informalexample, informalfigure, itemizedlist, legalnotice, listitem, meta (db.meta.content), msgexplan, msgtext, note, orderedlist, packagesynopsis, para, partintro, preface, procedure, qandadiv, qandaset, question, refsect1, refsect2, refsect3, refsection, refsynopsisdiv, result, revdescription, sect1, sect2, sect3, sect4, sect5, section, setindex, sidebar, simplesect, step, taskprerequisites, taskrelated, tasksummary, td, textobject, th, tip, toc, tocdiv, topic, variablelist, warning.


The following elements occur in unionsynopsis: info (db.titleforbidden.info), modifier, package, synopsisinfo, union, unionname.