XML — Entity Reference

Predefined Entities

Entity	Character	Description
<	<	Less than
>	>	Greater than
&	&	Ampersand
"	"	Double quote
'	'	Apostrophe

Using Entities

<text>Price: 5 &lt; 10 &amp; 10 &gt; 5</text>

Custom Entities

<!DOCTYPE note [
    <!ENTITY copyright "© 2025 Example Inc.">
    <!ENTITY company "ACME Corp">
]>
<note>
    <text>This is &copyright; by &company;</text>
</note>

Numeric Character References

<!-- Decimal -->
&#65;    <!-- A -->
&#169;   <!-- © -->

<!-- Hexadecimal -->
&#x41;   <!-- A -->
&#xA9;   <!-- © -->

CDATA Section

For content with many special characters:

<script>
<![CDATA[
    if (x < 10 && y > 5) {
        alert("Hello <world>");
    }
]]>
</script>

Entity Types

Type	Scope
Internal	Defined in DTD
External	Referenced file
Parameter	Used in DTD
General	Used in document

Best Practices

1. Use predefined entities for special characters
2. Use CDATA for code blocks
3. Define custom entities for reuse
4. Avoid external entities (security risk)

Mini Practice

1. Use all predefined entities
2. Create a custom entity
3. Use numeric character references
4. Write CDATA sections

Up Next

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