Infoset refers to a summary of definitions for uniform access to the various elements in an XML document. The corresponding recommendation was published by the Word Wide Web Consortium(W3C) in October 2001, differentiating eleven different types of information units, each with special properties. Accordingly, an Infoset comprises the hierarchical structure of information units, which can be of different types. An XML document that is well-formed and also satisfies the restrictions on the use of namespaces contains an Infoset. The node tree of the Document Object Model( DOM) as well as the data model of XPath do not fully represent the infoset.
The logical structure of an XML document consists of a tree of information units, the mapping of which is also called XML Information Set (Infoset). The Infoset is thus the basis for further recommendations of the W3C, all of which specify the structure and form of XML documents. The Infoset distinguishes the following eleven types of information units, each with special properties:
Document, Element, Attribute, Processing Instruction, Unresolved Entity Reference, Character, Comment, Document Type Declaration( DTD), Unparsed Entity, Notation, and Namespace.