XSLT - XML, XSL, and XSLT

XML, XSL, and XSLT are closely related but serve different purposes. 

1. XML (Extensible Markup Language)

  • What it is:
    A markup language used to store and transport structured data in a text format.

  • Purpose:
    Focuses on data representation — it defines what the data is.

  • Nature:
    Platform-independent, self-descriptive, and tag-based (like HTML but for data, not presentation).

Example (XML document):

<book>
  <title>1984</title>
  <author>George Orwell</author>
</book>

2. XSL (Extensible Stylesheet Language)

  • What it is:
    A family of languages designed to work with XML documents. It includes:

    • XSLT (Transformations)

    • XPath (Navigation within XML)

    • XSL-FO (Formatting Objects for print/pdf-style output)

  • Purpose:
    Defines how to style, format, or transform XML data.

  • Nature:
    Not a single language but a set of languages related to XML styling and transformation.

Think of XSL as the toolbox, while XSLT is one of the tools in that box.

3. XSLT (XSL Transformations)

  • What it is:
    A part of XSL — specifically the transformation language.

  • Purpose:
    Transforms XML data into other formats (HTML, another XML, plain text, JSON, etc.).

  • Nature:
    Written as XML itself, template-based, and uses XPath for navigation.

Example (XSLT stylesheet that transforms the book XML to HTML):

<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform" version="1.0">
  <xsl:template match="/">
    <html>
      <body>
        <h2>Book: <xsl:value-of select="book/title"/></h2>
        <p>Author: <xsl:value-of select="book/author"/></p>
      </body>
    </html>
  </xsl:template>
</xsl:stylesheet>

Comparison Table: XML vs XSL vs XSLT

Feature/Aspect XML XSL XSLT
Definition Data storage and transport format A family of languages for styling/transforming XML A transformation language (part of XSL)
Focus Describes data Describes how XML should be presented or processed Transforms XML into other formats
Type Markup language Specification (toolbox) Stylesheet-based transformation language
Output Raw structured data Styling rules (and formatting models) HTML, text, XML, JSON, etc.
Used With Any application needing structured data XML documents (to style/format them) XML + XSLT processor
Example Use Case Store a catalog of books Define print layout or styling Convert book catalog XML into an HTML webpage

In short:

  • XML = the raw data.

  • XSL = the language family for styling/transforming XML.

  • XSLT = the specific part of XSL used for transforming XML into other formats.