DTDs are the only finalised schema language for XML at present. Alternatives
such as DCD, XML-Data and XSchema are proposals still being developed
(although it looks like DCD replaces XML-Data).
(see http://www.schema.net/otherschemata/ for more information about these)
>2. Is there anywhere a clear documentation on DTD without diving
>into the whole SGML DTD stuff? I am lost between HTML4 DTD, SGML DTD and
>XML DTD.
A DTD tutorial will be available soon at schema.net
>3. The database I am working on is highly hierarchical. MS schema
>documentation describes uses SUPERTYPE to declare inheritance. Is there
>any equivalent DTD declaration?
You could achieve something like this by using a FIXED attribute on the
subtype. For example:
<!ELEMENT Person (#PCDATA)>
<!ELEMENT Employee (#PCDATA)>
<!ATTLIST Employee
SuperType NMTOKEN #FIXED "Person">
James