XML Information Set (XML Infoset) is aW3C specification that defines an abstractdata model of anXML document in terms of a set ofinformation items.[1] The XML Infoset provides a standardized way to refer to the components of XML documents, serving as a foundation for XML-related standards and tools.
The XML Infoset identifies eleven different types of information items, including the document, elements, attributes,processing instructions,characters, andnamespaces. Each information item has a set of named properties, which represent specific aspects of the XML document being modeled. For example, an element information item has properties such as the element's namespace name,local name,children, andattributes.
An XML document has an information set if it iswell-formed and satisfies thenamespace constraints. There is no requirement for an XML document to bevalid according to aDTD orXML Schema in order to have an information set.
XML was initially developed without a formal definition of its infoset. This conceptual foundation was only formalized by later work beginning in 1999, first published as a separate W3C Working Draft at the end of December that year.[2] The Infoset Recommendation Second Edition was adopted on February 4, 2004.[3]
The XML Information Set specification has become a cornerstone of the XML technology stack, enabling higher-level specifications such asXPath,XSLT,DOM,XQuery, and many others to describe their functionality in terms of the XML Infoset rather than the concrete XML syntax. This abstraction allows these technologies to operate on XML content regardless of its specific serialization format. If a 2.0 version of the XML standard is ever published, it is likely that this would absorb the Infoset recommendation as an integral part of that standard.
An information set can contain up to eleven different types of information items:
Infoset augmentation or infoset modification refers to the process of modifying the infoset duringschema validation, for example by adding default attributes. The augmented infoset is called the post-schema-validation infoset, orPSVI.[4]
Infoset augmentation is somewhat controversial, with claims that it is a violation of modularity and tends to cause interoperability problems, since applications get different information depending on whether or not validation has been performed.[5]
Infoset augmentation is supported byXML Schema but notRELAX NG.
Typically, XML Information Set is serialized as XML.[6] There are also serialization formats forBinary XML,CSV,[7] andJSON.[8]
XML Information Set instances:
 | ThisWorld Wide Web–related article is astub. You can help Wikipedia byadding missing information. |