DTD stands for Document Type Definition. It is a document that defines the structure of an XML document. It is used to describe the attributes of the XML language precisely. It can be classified into two types namely internal DTD and external DTD. It can be specified inside a document or outside a document. DTD mainly checks the grammar and validity of an XML document. It checks that an XML document has a valid structure or not.
Characteristics
- It defines the compulsory and optional elements in the XML document.
- It validates the structure of the XML document.
- It check for the grammar of the XML document.
- It describes the order in which the element occurs.
Advantages
- We can define our own format for the XML files by DTD.
- It helps in validation of XML file.
- It provides us with a proper documentation.
- It enables us to describe a XML document efficiently.
Disadvantages
- DTDs are hard to read and maintain if they are large in size.
- It is not object oriented.
- The documentation support is limited.
- DTD doesn’t support namespaces.