• Source: XML Information Set

      • 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. 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.
      An information set can contain up to eleven different types of information items:

      The Document Information Item (always present)
      Element Information Items
      Attribute Information Items
      Processing Instruction Information Items
      Unexpanded Entity Reference Information Items
      Character Information Items
      Comment Information Items
      The Document Type Declaration Information Item
      Unparsed Entity Information Items
      Notation Information Items
      Namespace Information Items
      XML was initially developed without a formal definition of its infoset. This was only formalised by later work beginning in 1999, first published as a separate W3C Working Draft at the end of December that year.
      Infoset recommendation Second Edition was adopted on 4 February, 2004. 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.


      Infoset augmentation


      Infoset augmentation or infoset modification refers to the process of modifying the infoset during schema validation, for example by adding default attributes. The augmented infoset is called the post-schema-validation infoset, or PSVI.

      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.

      Infoset augmentation is supported by XML Schema but not RELAX NG.


      Serialization


      Typically, XML Information Set is serialized as XML. There are also serialization formats for Binary XML, CSV, and JSON.


      See also


      XML Information Set instances:

      Document Object Model
      Xpath data model
      SXML


      References




      External links


      "XML Information set recommendation (Second Edition)". W3C. 4 February 2004.

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