The meaning of any XML element can only be determined by finding the specification of the XML vocabulary that it belongs to. Different people can use the same element name to mean different things. If the vocabulary is widely used it will probably be in a namespace, and the namespace will then have a public definition that you can refer to. Without a specification of the particular vocabulary, there's no way of guessing.
Author, XSLT Programmer's Reference and XPath 2.0 Programmer's Reference