XML - XML Linking

What is XML?

XML stands for eXtensible Markup Language. It's used to store and transport data. XML doesn’t DO anything — it just holds data in a structured format that both humans and machines can read.

Example:

<student>
  <name>John</name>
  <age>20</age>
</student>

What is XML Linking?

Just like you can add links to webpages using HTML (like <a href="...">), XML allows you to link different parts of XML documents — or even link to other documents. This is called XML Linking.

XML Linking is done using XLink, XPointer, and sometimes XInclude.

Components of XML Linking

Let’s break it into 3 main concepts:

1. XLink (XML Linking Language)

XLink is a standard that allows elements in XML to behave like hyperlinks.

Types of links:

Type	Description
Simple Link	Like HTML's `<a>` tag. Links from one resource to another.
Extended Link	Links from one element to multiple resources or from multiple elements to one.

Example of Simple XLink:

<book xmlns:xlink="http://www.w3.org/1999/xlink" 
      xlink:href="http://example.com/book1" 
      xlink:type="simple">
  Learn XML
</book>

Here, the book element acts like a hyperlink.

2. XPointer (XML Pointer Language)

XPointer is used to point to specific parts inside an XML document, like jumping to a particular paragraph in a book.

Example:

xlink:href="book.xml#xpointer(/bookstore/book[1]/title)"

This means: go to book.xml and get the title of the first book.

Think of it like a GPS for XML — it helps you find exactly where something is in the file.

3. XInclude (XML Inclusion)

XInclude is used when you want to include one XML document inside another.

Example:

<xi:include href="chapter1.xml" xmlns:xi="http://www.w3.org/2001/XInclude" />

This means: "Include the content of chapter1.xml here".

Why Use XML Linking?

To reuse content from other XML documents
To connect related data
To build complex XML documents from smaller ones
To improve organization and readability