Notation declarations provide labels for content in a document. The XML Recommendation [XML] requires that the DTD contain all notation declarations for a document. You use notations to identify file types or for a variety of other tasks. Notations can identify the following items by name:
The format of unparsed entities
The format of elements that bear a notation attribute
The application to which a processing instruction is addressed
Notation declarations provide a name for the notation, which you can then use in entity and attribute-list declarations and specifications. Notation declarations can also provide a name for an external identifier for the notation that allows an XML processor or its client application to ...