Introduction to XML

2 min read 2 runnable examples Quiz included

XML (eXtensible Markup Language) is a format for storing and exchanging structured data. It looks like HTML, but instead of predefined tags, you invent tags that describe your data.

XML

<?xml version="1.0" encoding="UTF-8"?>
<book>
  <title>Learning Python</title>
  <author>Mark Lutz</author>
  <year>2013</year>
  <price currency="USD">44.99</price>
</book>

Press Run: CodeMIRAI checks the document with a real XML parser and shows its structure.

XML vs HTML

	HTML	XML
Purpose	display a page	describe and carry data
Tags	predefined (`<p>`, `<h1>`)	you invent them (`<book>`, `<price>`)
Errors	browsers guess and carry on	a mistake makes the whole document invalid

Where XML is used

Where	Examples
Office files	`.xlsx`, `.docx` and `.pptx` are zipped folders of XML
Configuration	Android layouts, Maven's `pom.xml`, .NET config files
Web feeds	RSS and Atom
Graphics	SVG images are XML
Data exchange	banking, healthcare and government systems (SOAP web services)

A document with repeating data

XML

<?xml version="1.0" encoding="UTF-8"?>
<library>
  <book id="1">
    <title>Clean Code</title>
    <author>Robert C. Martin</author>
  </book>
  <book id="2">
    <title>The Pragmatic Programmer</title>
    <author>Andrew Hunt</author>
  </book>
</library>

Each <book> has the same structure, which makes the data easy for programs to read.

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