A content model is the description of the structure
and content of an element that is used to validate an XML instance document.
XML Schema content models offer more control on element occurrences than DTD
In addition, schema content models allow the validation of mixed content.
A content model can restrict an XML instance document to a certain set of
element types and attributes,
describe and constrain the relationships between these different components,
identify specific elements.
Sharing these content models allow businesses to exchange structured