What's the difference between an element and a node in XML?

xml xmlnode

I'm working in Java with XML and I'm wondering; what's the difference between an element and a node?

Great comment from forums.asp.net/t/443912.aspx/1#443940: The same as between fruit and apple. Every XmlElement is XmlNode, but not every XmlNode is XmlElement. XmlElement is just one kind of XmlNode. Others are XmlAttribute, XmlText etc.

An Element is part of the formal definition of a well-formed XML document, whereas a node is defined as part of the Document Object Model for processing XML documents.

Benoit

The Node object is the primary data type for the entire DOM.

A node can be an element node, an attribute node, a text node, or any other of the node types explained in the "Node types" chapter.

An XML element is everything from (including) the element's start tag to (including) the element's end tag.

Now that I understand the answer...The convention is stupid. The words should be the other way around. In natural English language an 'element' is something which is the most basic building block, out of which everything else is built. i.e. an element in natural English is more general...

@Juan Mendes: That's what they are according to the DOM, but Sam's point is that the DOM considers nodes more basic (primitive) than elements, when "element" actually refers to the most basic building block in English.

@SamSvenbjorgchristiensensen that's not quite accurate. Elements can be broken down further into 'constituent parts' like protons, neutrons and electrons, which in turn can be broken into quarks, neutrinos, etc. It's better to understand what a 'node' means in graph theory, and then you'll understand why the XML designers chose that name (the DOM is just a hierarchical graph).

@LesHazlewood Actually, the word "element" was used to describe physical elements (hydrogen, helium, etc) because they did think those things were indivisible. It was only much later they found out they were wrong - far too late to change the name ; ) I agree with Sam, the way they named and differentiated dom elements vs nodes is confusing and poorly thought through (as much of the html spec is).

@BT your argument would hold water if the XML spec committee lived in ancient Greece :) They did not, and as such, the modern (dictionary) definition of element that (clearly) represents constituent parts makes sense. Add that with graph theory knowledge of nodes, and there's really not much room for interpretation.

Bobby

Different W3C specifications define different sets of "Node" types.

Thus, the DOM spec defines the following types of nodes:

Document -- Element (maximum of one), ProcessingInstruction, Comment, DocumentType

DocumentFragment -- Element, ProcessingInstruction, Comment, Text, CDATASection, EntityReference

DocumentType -- no children

EntityReference -- Element, ProcessingInstruction, Comment, Text, CDATASection, EntityReference

Element -- Element, Text, Comment, ProcessingInstruction, CDATASection, EntityReference

Attr -- Text, EntityReference

ProcessingInstruction -- no children

Comment -- no children

Text -- no children

CDATASection -- no children

Entity -- Element, ProcessingInstruction, Comment, Text, CDATASection, EntityReference

Notation -- no children

The XML Infoset (used by XPath) has a smaller set of nodes:

The Document Information Item

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

XPath has the following Node types:

root nodes

element nodes

text nodes

attribute nodes

namespace nodes

processing instruction nodes

comment nodes

The answer to your question "What is the difference between an element and a node" is:

An element is a type of node. Many other types of nodes exist and serve different purposes.

mmaibaum

A Node is a part of the DOM tree, an Element is a particular type of Node

e.g. <foo> This is Text </foo>

You have a foo Element, (which is also a Node, as Element inherits from Node) and a Text Node 'This is Text', that is a child of the foo Element/Node

This short example gives me more understanding then the selected answer.

Greg Hewgill

A node can be a number of different kinds of things: some text, a comment, an element, an entity, etc. An element is a particular kind of node.

fenomas

As described in the various XML specifications, an element is that which consists of a start tag, and end tag, and the content in between, or alternately an empty element tag (which has no content or end tag). In other words, these are all elements:

<foo> stuff </foo>
<foo bar="baz"></foo>
<foo baz="qux" />

Though you hear "node" used with roughly the same meaning, it has no precise definition per XML specs. It's usually used to refer to nodes of things like DOMs, which may be closely related to XML or use XML for their representation.

Colonel Panic

An xml document is made of nested elements. An element begins at its opening tag and ends at its closing tag. You're probably seen <body> and </body> in html. Everything between the opening and closing tags is the element's content. If an element is defined by a self-closing tag (eg. <br/>) then its content is empty.

Opening tags can also specify attributes, eg. <p class="rant">. In this example the attribute name is 'class' and its value 'rant'.

The XML language has no such thing as a 'node'. Read the spec, the word doesn't occur.

Some people use the word 'node' informally to mean element, which is confusing because some parsers also give the word a technical meaning (identifying 'text nodes' and 'element nodes'). The exact meaning depends on the parser, so the word is ill-defined unless you state what parser you are using. If you mean element, say 'element'.

The word does occur: "(i.e., each leaf node in the syntax tree for the regular expression)". It's in a non-normative appendix, but nevertheless it does occur. There the term is used as node in the parse tree.

Even if one considers that the XML definition does not mention nodes, the Document Object Model (DOM) defined for programmatic interpretation and manipulation of XML (by the same standards organization) does indeed define and use the term "node". This answer does not help to differentiate the terms and it does not help to just ignore the various uses by asserting that they mean the same thing.

Troels Thomsen

A node is the base class for both elements and attributes (and basically all other XML representations too).

eugensk

Element is the only kind of node that can have child nodes and attributes.

Document also has child nodes, BUT no attributes, no text, exactly one child element.

Robert Rocha

A node is defined as:

the smallest unit of a valid, complete structure in a document.

or as:

An object in the tree view that serves as a container to hold related objects.

Now their are many different kinds of nodes as an elements node, an attribute node etc.

佚

佚名

Now i know ,the element is one of node

All node types in here"http://www.w3schools.com/dom/dom_nodetype.asp"

Element is between the start tag and end in the end tag

So text node is a node , but not a element.

Simon Keep

An element is a type of node as are attributes, text etc.

Sabique A Khan

XML Element is a XML Node but with additional elements like attributes.

<a>Lorem Ipsum</a>  //This is a node

<a id="sample">Lorem Ipsum</a>  //This is an element

I don't assume you have any source for this claim? For example the XML standard defines the term "element" being either an empty element tag or everything from and including the start tag to and including the end tag. A start tag and empty element tag does not need to have any elements. Both your examples are elements. The term "node" is defined elsewhere, in DOM which is about an object model and not in the text itself.

Purna

node & element are same. Every element is a node , but it's not that every node must be an element.

As "it's not that every node must be an element", the claim "node & element are same" is wrong.

Besides your description is wrong, it's not very useful either. The only thing you're correct about is that there is some difference between the terms, but the question was what difference there is.

What's the difference between an element and a node in XML?

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