Disadvantages of DTDs

• Limited Data Types: DTDs offer only basic data type support compared to more modern schema languages like XML Schema (XSD).
• Complex Validation Rules: DTDs are less suitable for defining complex validation rules and constraints.
• No Support for Namespace: DTDs do not support XML namespaces.

Document Type Definitions (DTDs) are a fundamental component of XML, providing a means to define and validate the structure of XML documents.

DTD stands for Document Type Definition. It is a set of rules which is used to define the structure and elements of an XML document. A DTD:

• Specifies which elements are allowed in the document
• Order in which they should appear
• Data types for attribute values

DTDs are used to validate and describe the structure of XML documents. In a way, they are a set of rules that confirm that the XML document follows a specified structure.