# The NodeInfo interface

The NodeInfo object represents a node of an XML document. It has a subclass `DocumentInfo` to represent the root node, but all other nodes are represented by `NodeInfo` itself. These follow the XPath data model closely.

In earlier releases, `NodeInfo` extended the DOM interface `Node`. This is no longer the case; it has been changed to make it easier to integrate Saxon with other XML tree representations such as JDOM. Until Saxon 8.2, the main Saxon implementations of the `NodeInfo` interface continued to also implement the DOM `Node` interface, but this is no longer the case from Saxon 8.3 onwards: it has been changed because the DOM interface was becoming increasingly unwieldy, and in particular because it is incompatible between JDK 1.4 and JDK 1.5. Instead, a new class `NodeOverNodeInfo` is provided, which presents a DOM view of a Saxon node.

The `NodeInfo` object provides the application with information about the node. The most commonly used methods include:

getNodeKind() | gets a short identifying the node type (for example, element or attribute). The values are consistent with those used in the DOM, and are referenced by constants in the class `net.sf.saxon.value.Type`
getDisplayName(), getLocalPart(), getPrefix(), getURI() | These methods get the name of the element, or its various parts. The getDisplayName() method returns the QName as used in the original source XML.
getAttributeValue() | get the value of a specified attribute, as a String.
getStringValue() | get the string value of a node, as defined in the XPath data model
getTypedValue() | get the typed value of a node, as defined in the XPath 2.0 data model. This is in general a sequence of atomic values, so the result is a `SequenceIterator`.
getParent() | get the `NodeInfo` representing the parent element, (which will be a `DocumentInfo` object if this is the outermost element).

iterateAxis()

returns an SequenceIterator object that can be used to iterate over the nodes on any of the XPath axes. The first argument is an integer identifying the axis; the second is a `NodeTest` (a simple form of pattern) which can be used to filter the nodes on the axis. Supply `null` if you want all the nodes on the axis. (For most applications, it is probably simpler to navigate from a node by compiling an XPath expression, and executing it with the correct starting node as the context node).

For other methods, see the JavaDoc documentation.

It is possible (though not easy) to provide your own implementation of the `NodeInfo` interface, perhaps allowing Saxon queries to run directly against some non-XML data source. There are helper methods in the `net.sf.saxon.om.Navigator` class that reduce the amount of code you need to write to achieve this. See the implementations that map `NodeInfo` to DOM, DOM4J, JDOM or XOM to see how it is done.