xml-dev - Re: DTD vs Schema

["James Tauber" <jtauber@jtauber.com>]

-----Original Message-----
From: AMER, Nidal <Nidal.AMER@hdmp.com>
>1. What is the right way to describe XML message syntax: DTD or
>schema. I started by looking at Microsoft site. The publish
>documentation on schema but nothing about DTD. They also say schema is a
>better way to describe XML as it is XML.

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


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