The W3C XML Schema Language (often misleadingly labeled simply “schemas”) is a very powerful but very complex language. The primary feature of this language, relative to other schema languages, is data typing, especially for attribute values and simple element text. This language can state that a particular element or attribute contains an int, a date, a string, a double, a qualified name, a positive integer, and so on. Beyond the 42 simple types it defines, developers can extend the language with their own types such as money, phone number, color, and more.
Key features of this language include the following:
Validation of element and attribute structures by complex types
Validation of text content by simple data types ...