XML Information Set (XML Infoset) is a W3C specification describing an abstract data model of an XML document in terms of a set of information items.[1] The definitions in the XML Information Set specification are meant to be used in other specifications that need to refer to the information in a well-formed XML document.

An XML document has an information set if it is well-formed and satisfies the namespace constraints. There is no requirement for an XML document to be valid in order to have an information set.