XML `Tree Structure`

XML documents form a tree structure that starts at the "root" and extends to the "leaves."

An XML Document Example

XML documents use a simple, self-descriptive syntax:

<?xml version="1.0" encoding="UTF-8"?>
<note>
<to>Tove</to>
<from>Jani</from>
<heading>Reminder</heading>
<body>Don't forget me this weekend!</body>
</note>

The first line is the XML declaration. It defines the XML version (1.0) and the encoding used (UTF-8: Unicode, capable of displaying various languages).

The next line describes the root element (as if saying, "This document is a note"):

<note>

The following four lines describe the four child elements of the root (to, from, heading, and body):

<to>Tove</to>
<from>Jani</from>
<heading>Reminder</heading>
<body>Don't forget me this weekend!</body>

The last line defines the end of the root element:

</note>

You can infer from this example that the XML document contains a note from Jani to Tove.

XML boasts excellent self-descriptiveness, don't you agree?

XML Documents Form a Tree Structure

An XML document must contain a root element. This element is the parent of all other elements.

Elements in an XML document form a document tree. This tree starts at the root and extends to the bottom of the tree.

All elements can have child elements:

<root>
<child>
<subchild>.....</subchild>
</child>
</root>

Terms like parent, child, and sibling are used to describe the relationships between elements. A parent element has child elements. Child elements at the same level are siblings (brothers or sisters).

All elements can have text content and attributes (similar to HTML).

Example:

The diagram represents a book from the following XML:

XML Document Example

<bookstore>
    <book category="COOKING">
        <title lang="en">Everyday Italian</title>
        <author>Giada De Laurentiis</author>
        <year>2005</year>
        <price>30.00</price>
    </book>
    <book category="CHILDREN">
        <title lang="en">Harry Potter</title>
        <author>J K. Rowling</author>
        <year>2005</year>
        <price>29.99</price>
    </book>
    <book category="WEB">
        <title lang="en">Learning XML</title>
        <author>Erik T. Ray</author>
        <year>2003</year>
        <price>39.95</price>
    </book>
</bookstore>

The root element in the example is <bookstore>. All <book> elements are contained within <bookstore>.

The <book> element has four child elements: <title>, <author>, <year>, <price>.

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XML Tree Structure

An XML Document Example

XML Documents Form a Tree Structure

Example:

XML Document Example

XML `Tree Structure`