XML Data Formatter

announcement: this doc is a quiz-, interview-oriented cheatsheet, which is designed for those who want to have an overview of XML, when preparing for interviews.

What is XML

XML stands for eXtensible Markup Language. XML was designed to store and transport data. XML is often used for distributing data over the Internet (especially in web development).

How XML Stores Data

XML uses a DTD or schema to describe the data.

XML and HTML

XML: is used to store or transport data. XML is a complement to HTML.
HTML: is used to format and display the same data.

XML does not carry any information about how to be displayed. The same XML data can be used in many different presentation scenarios. Because of this, with XML, there is a full separation between data and presentation.

XML Schema/DTD

The purpose of a DTD or schema is to define the structure of an XML document. It defines the structure with a list of legal elements.

When Not to Use XML DTD/Schema

XML does not require a DTD or schema.

When you are experimenting with XML, or when you are working with small XML files, creating DTDs may be a waste of time.

If you develop applications, wait until the specification is stable before you add a document definition. Otherwise, your software might stop working because of validation errors.

XML Syntax

The XML language has no predefined tags, but the syntax is rather logical and easy to learn. XML documents must contain one root element that is the parent of all other elements.

<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>Erik T. Ray</author>
    <year>2003</year>
    <price>39.95</price>
  </book>
</bookstore>

Key XML Syntax Rules

XML tags are case-sensitive.
All XML elements must have a closing tag.

<p>This is a paragraph.</p>
<br />  <!-- This is a self-closing tag -->

XML attribute values must always be quoted.
Pay attention to the naming rules for elements and attributes.

XML Data Formatter - Learn XML Syntax and Structure