Designing Your own XML Schema: Learn the Essentials:
What is XML Schema and why does it exist?
XML documents (or files with the extension “.xml”) are designed with no rules and regulations by default. Don’t be misled by the phrase “no rules and regulations.” In this sense, I mean that it is “highly customizable.” That means no one in this world can constrain or stop you from defining your own “markup” language. You can start with your own elements, attributes, and values along with your own structure.