XML Syntax

Rules of the eXtensible Markup Language (XML)

All XML elements must have a closing tag
```
<p>This is a paragraph</p>
```
Comments in XML
```

```

XML tags are case sensitive

<TITLE>This example is incorrect</title>  <!-- INCORRECT -->

<title>This example is correct</title>

XML elements must be properly nested

<strong><em>This text is important and emphasized</strong></em>
    <!-- INCORRECT because closing em tag appears out of order -->

<strong><em>This text is important and emphasized</em></strong>

XML documents must have a root element

XML documents must contain one element that is the parent of all other elements. This element is called the root element.
```
<html>
  <head>
    <title>Title</title>
  </head>
</html>
```

XML attribute values must be quoted

<img src=image.png/> <!-- INCORRECT because `image.png` is not quoted -->

<img src="image.png">

Special characters in XML

<code>if salary < 1000:</code> <!-- INCORRECT because `<` confused with
                                    start of tag -->

<code>if salary &lt; 1000:</code>

Entity	Symbol	Description
<	<	less than
>	>	greater than
&	&	ampersand
'	’	apostrophe
"	”	quotation mark

Practice

Syntax

Identify the two XML errors in each of the following examples and correct them. (solutions)

<?xml version="1.0"?>

<bookstore>
  <book category="CHILDREN">
    <title>Harry Potter</title>
    <Author>J K. Rowling</author>
    <year>2005</year>
    <price>29.99</price>
  </book>
  <book category=WEB>
    <title>Learning XML</title>
    <author>Eric T. Ray</author>
    <year>2003</year>
    <price>39.95</price>
  </book>
</bookstore>

Element names are case sensitive – <Author> should be <author>
Attribute values must be quoted – category="WEB"

<?xml version="1.0"?>

<book category="CHILDREN">
  <title>Harry Potter</title>
  <author>J K. Rowling</author>
  <year>2005</year>
  <price>29.99</price>
</book>
<book category="WEB">
  <title>Learning XML</title>
  <author>Eric T. Ray & John S. Green</author>
  <year>2003</year>
  <price>39.95</price>
</book>

XML documents must have a single root element
XML entities (i.e., &) must be escaped – &

<?xml version="1.0"?>

<bookstore>
<book category="CHILDREN">
  <title>Harry Potter</title>
  <author>J K. Rowling</author>
  <year>2005<month>August</year></month>
  <price>29.99</price>
</bookstore>

XML tags must be closed – missing </book> before </bookstore>
XML tags must be nested correctly – close year tag before month

Design

Design an XML document to track a triathlon race. Racers have a number, first name, last name, and race times for swimming, biking, and running.