Although there is no consensus on the terminology used on XML Trees, at least two standard terminologies have been released by the W3C: XPath defines a syntax named XPath expressions that identifies one or more internal components (elements, attributes, etc.)
In mathematics, a tree is an undirected graph in which any two vertices are connected by exactly one simple path.
This specification is long, however 2 key points relating to the tree structure of an XML document are: These features resemble those of trees, in that there is a single root node, and an order to the elements.
The tree command in Windows and *nix also produce a similar tree structure and path.XPath, the XML Path Language, is a query language for selecting nodes from an XML document.
XPath is widely used in other core-XML specifications and in programming libraries for accessing XML-encoded data.
[2] The XPath Data Model is a long specification, and goes into many features unrelated to XML trees.
An XML document has an information set if it is well-formed and satisfies the namespace constraints.
An element information item has the following properties: There is an attribute information item for each attribute (specified or defaulted) of each element in the document, including namespace declarations.