When a number of documents have similar or identical structures, they should naturally contain the same element types. Furthermore, they should be considered to be a group of documents that both define and conform to the same document class, or document model.
For example, all news items would include a location, a source and the name of the writer, so they all conform to the same model. A document model provides the technical specification of an XML application, such as XMLNews-Story. This particular model defines a number of element types, including the following:
Nitf (news item)
Body (body of the news item)
Title (title of the news item)
Byline (writer of the news item)
Dateline (date the item was submitted).
Similarly, a model ...