This function returns 1 if the tag specified by tagname is declared as a hidden element in the document type configuration file (.dcf) for the document type associated with doc. If doc is 0 or omitted, the current document is used.

A hidden tag is one that does not display in Arbortext Editor dialog boxes that provide lists of DTD tags , such as the Find Tag/Attribute dialog box). However, a hidden tag is returned when you request a list of elements in a document type are requested (for example, when calling the tag_names function). Also, hidden tags are automatically excluded by the exclude_tag callback.