XML-Schema XML Schema is a relatively new schema language developed and endorsed by the W3C to address the shortcomings of DTDs. XML is written in XML itself, which means it can be parsed with a XML parser. XML Schema allows you to define both global and local variables. It also contains a system of data types which allow you to specify that an element must contain an integer, float, double, date, string, etc.... XML Schema also allows for the use of namespace declarations. In short, XML Schema gives you a lot of control over the content of an XML document.