Question

What is meant by Internal DTD?

Answer 1

here is your answer

The document type (DOCTYPE) declaration consists of an internal, or references an external Document TypeDefinition (DTD). It can also have a combination of both internal and external DTDs. The DTD defines the constraints on the structure of an XML document.
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Answer 2

hey dear your answer is here..

Internal DTD. A DTD is referred to as an internal DTD if elements are declared within the XML files. To reference it as internal DTD, standalone attribute in XML declaration must be set to yes. This means the declaration works independent of external source.