Describe the differences between the Document Type Definition (DTD) and the XML Schema.

Question

What will be an ideal response?

Answer 1

While XML 1.0 supplies the DTD mechanism for defining the content model (the valid order
and nesting of elements) and, to a limited extent, the data types of attributes of an XML
document, it has a number of limitations:
? it is written in a different (non-XML) syntax;
? it has no support for namespaces;
? it only offers extremely limited data typing.
The W3C XML Schema overcome these limitations and is much more expressive than DTDs.
An XML schema is the definition (both in terms of its organization and its data types) of a
specific XML structure. The W3C XML Schema language specifies how each type of element
in the schema is defined and what data type that element has associated with it. The schema is
itself an XML document, using elements and attributes to express the semantics of the
schema. As it is an XML document, it can be edited and processed by the same tools that read
the XML it describes.