🚀 go-pugleaf

In SGML inclusions are defined: this allows logical elements to appear
anywhere in the tree-structure starting from some specific node. Also,
references to logical elements are defined. Is something like these
concepts also defined in ODA? For example, in SGML you can specify the
following logical structure:

	<!element chap   (title, par*)   +(figure) >
	<!element par   (#PCDATA|figref)* >

	<!element figref EMPTY >
	<!attlist figref ref IDREF #IMPLIED >

	<!element figure ... >
	<!attlist figure id  ID    #IMPLIED >

The first line defines an inclusion ('+(figure)'): it means that
anywhere in the subtree starting at element 'chap' (chapter) the
element 'figure' may appear. A paragraph is defined as zero or more
instances of data or figref. Element 'figref' (reference to a figure)
has no content (is EMPTY) and has an attribute that has a reference as
its value (the precise value is IMPLIED by the application). Element
'figure' also has an attribute, which has some unique value (an
IDentifier, also IMPLIED by the application). 'figref' can be used as
a reference to a specific figure, by using the value of attribute 'id'
of that figure as the value of attribute 'idref'.

Does ODA have equivalent concepts? If so, where is it described, how
does one use it in a layout specification? If not, how does one specify
the above example in ODA? Please mail any answers.

			Frans Heeman
			Dept. of Mathematics and Computer Science
			Free University Amsterdam
			de Boelelaan 1081
			1081 HV  Amsterdam
			The Netherlands.

			email: frans@cs.vu.nl