In: Computer Science
Answer)
A document type declaration or DOCTYPE is the instruction which is associated with an SGML or XML document and also a webpage to depict a document type definition (DTD) so that the markup detects it to be in a particular syntax. For example, in an HTML page web browsers performs the sniffing for the DOCTYPE, where the DOCTYPE = "text/html" determines that it is an HTML layout mode.
There are many types of XML documents, and one of those types of XML document contains the data and is known as the Instance Document. The Instance document consists of the data elements embedded in the XML document which will consist of information such as financial information of a company. The Instance documentation is a combination of XML and data, and the document stores data such that it is possible for machine recognition as well as it is human readable.