XML tree

XML documents have a hierarchical structure and can conceptually be interpreted as a tree structure, called an XML tree.

XML documents must contain a root element (one that is the parent of all other elements). All elements in an XML document can contain sub elements, text and attributes. The tree represented by an XML document starts at the root element and branches to the lowest level of elements. Although there is no consensus on the terminology used on XML Trees, at least two standard terminologies have been released by the W3C:

• The terminology used in the XPath Data Model
• The terminology used in the XML Information Set.

XPath defines a syntax named XPath expressions that identifies one or more internal components (elements, attributes, etc.) of an XML document. XPath is widely used to accesses XML-structured data.

The XML Information Set, or XML infoset, describes an abstract data model for XML documents in terms of information items. It is often used in the specifications of XML languages, for its convenience in describing constraints on constructs those languages allow.