Xml - Infoset

About

The XML Infoset:

• is a tree-based hierarchical representation of an XML document.
• is the abstract data and metadata (ie abstract means independently of this representation, independent of the actual technical implementation)
• represents the significant informations of an XML document

Just because an XML document is an infoset does not mean it conforms to an XSD and is a valid XML document.

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Types of information items

An XML document's information set consists of a number of information items.

The information set for any well-formed XML document will contain at least a document information item and several others.

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

There are information items representing:

• the document,
• its elements,
• attributes,
• processing instructions,
• comments,
• characters,
• notations,
• namespaces,
• unparsed entities,
• unexpanded entity references,
• and the document type declaration

Representation

XML is just one way of representing that data.

The infoset may exist:

• in memory as a DOM tree
• in a XML encoded in UTF-8 or in UTF-16.
• …

For example, the infoset does not distinguish between the two forms of empty element.

The following are considered equivalent according to the XML Infoset.

<test></test>
<test/>

Augmentation

Infoset augmentation or infoset modification refers to the process of modifying the infoset during schema validation, for example by adding default attributes.

Documentation / Reference

• Understanding Infosets
• XML Information Set Specification