Editing XML schema (section)

== Validation ==
The process of checking to see if a XML document conforms to a schema is called [[XML validation|validation]], which is separate from XML's core concept of syntactic [[Well-formed document|well-formedness]]. All XML documents must be well-formed, but it is not required that a document be valid unless the XML parser is "validating", in which case the document is also checked for conformance with its associated schema. DTD-validating [[Parsing|parser]]s are most common, but some support XML Schema or RELAX NG as well.

Validation of an instance document against a schema can be regarded as a conceptually separate operation from XML parsing. In practice, however, many schema validators are integrated with an XML parser.