Content model for the <graphic> element
This is a very permissive model, allowing almost anything that could be inside a full Figure. In most cases, the <graphic> element will be empty, with attributes pointing to an external file.
<!ENTITY % graphic-model "(%access.class; | %address-link.class; | %id.class; | %label.class; | %caption.class; | %display-back-matter.class;)* " >
(alt-text | long-desc | email | ext-link | uri | object-id | label | caption | attrib | permissions)*