HTML Vs XML - Whats The Difference?

Introduction

In this article, we will understand the difference between HTML and XML.

What is HTML?

HTML stands for Hypertext Markup Language. HTML is the most widely used language for developing web applications. HTML5 is the current version and was published in 2012. It is used to create websites and web applications. Let's break it down better to understand the name- Hypertext, or "hypertext," refers to the "text wrapped within a text." It is similar to a hyperlink in that it contains underlying text that, when clicked, redirects to a different webpage. Markup Language, A markup language is not necessarily a programming language.

Instead, it is used to apply formatting and layout to a simple text document. This leads to more interactive and dynamic text content. Web page, A web page is a document that is commonly coded in HTML and rendered by a web browser. A URL identifies every web page and can be static or dynamic according to the requirements. We can create static web pages if we only use HTML for development.

Get started with HTML by reading this detailed article- HTML For Beginners

HTML Tags

<!Doctype html> declaration updates the browser about the HTML version.

<html> tag encapsulates the complete web page content. All other tags are 'nested' in the <html> tag. Any HTML document or web page consists of two main sections.

<head></head>
<body></body>
<title> defines the title that should be displayed on the browser tab.
<meta> used to specify page description, author of the document, last modified, etc.
<style> defines style information for the web page.
<link> defines a link to other documents like CSS.
<script> defines script like JS.

HTML Elements

There are two types of HTML elements.

Container elements containing start tag < > and end tag </>.

e.g., h1, h2, form, p, div, etc.

Empty elements are those standalone tags that are considered to be self-closing tags. Empty elements will not enclose any content.

e.g., br, img, etc.

HTML Attributes

HTML elements can contain attributes that can be considered an additional feature to set various properties, and they are optional- Some of the attributes can be used with any HTML elements. There can be referred to as "global attributes" Also, some attributes can be used only with particular elements.

All the Attributes can contain properties like name and value which a developer can use to assign respective details for the HTML elements.

Attributes are used only under the start tag.

e.g.
Syntax- <html lang="en-us"> Specifies that the content of the HTML page is written in the US version of English.

<html>
  <head>
    <title> Test Page </title>
    <meta name="description" content="This is a test web page." />
    <meta name="keyword" content="HTML, XML" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
  </head>
  <body>
    <p>This is a test web page.</p>
  </body>
</html>

What is XML?

XML stands for an extensible markup language. XML is a markup language that defines a set of rules for encoding documents in a human-readable and machine-readable format.

Get a complete understanding of XML with our detailed article- Introduction To XML.

<?xml version="1.0" encoding="UTF-8"?>
<friendsList>
   <friend>
      <name>Alex</name>
   </friend>
   <friend>
      <name>Mery</name>
   </friend>
   <friend>
      <name>Rachel</name>
   </friend>
   <bestFriend>
      <name>Ana</name>
   </bestFriend>
</friendsList>

Let us discuss the above-written XML code. I created a tag called friendsList, which comes inside conical brackets, and then I created an end tag for friendsList. Now, inside this, I have created one more tag called friend. I have a start friend tag and an end friend tag; the end friend tag has a forward slash and the same name as the start friend tag. Inside this, I created a tag for the name and then gave the value to a friend named Alex similarly. I have created data for one more friend, Mary, and then one more for Rachel, so I have created data for three friends.

I have also created a tag for "bestFriend," where I gave her the name Ana. This is a more formatted and structured way of communicating and exchanging data, and it can be used to communicate between applications and is valid XML.

XML is known as a markup language because we use marks, or tags, as we have seen in our example, and the tags are not predefined like in HTML.
We can use tags that can be extended, like friendList, friend, name, etc., so tags are extensible, and therefore we call it extensible markup language.

Data Exchange and Communication In XML

XML can be used for data exchange and communication between two applications. It is possible to have both client and server applications. XML is used to store and transport data, and the rules and specifications of XML come from the World Wide Web Consortium. XML is not dependent on any platform or technology. So we can use two applications built over different platforms and different technology stacks, and they can communicate using XML, which is both human and machine-readable.

XML Validation

When we talk about validation, we are talking about validating the syntax and structure of our XML message, so we check that the XML is well-formed and satisfies all of the basic syntax, rules, and conditions. Then we can also check our XML against some predefined schema, which can be a DTD (Document Type Definition) or an XSD (XML Schema Definition).

Generated XSD

<xs:schema attributeFormDefault="unqualified" elementFormDefault="qualified" xmlns:xs="http://www.w3.org/2001/XMLSchema">
  <xs:element name="friendsList">
    <xs:complexType>
      <xs:sequence>
        <xs:element name="friend" maxOccurs="unbounded" minOccurs="0">
          <xs:complexType>
            <xs:sequence>
              <xs:element type="xs:string" name="name"/>
            </xs:sequence>
          </xs:complexType>
        </xs:element>
        <xs:element name="bestFriend">
          <xs:complexType>
            <xs:sequence>
              <xs:element type="xs:string" name="name"/>
            </xs:sequence>
          </xs:complexType>
        </xs:element>
      </xs:sequence>
    </xs:complexType>
  </xs:element>
</xs:schema>

Difference between HTML and XML

Key Attributes	HTML	XML
Full Form	Hyper Text Markup Language	Extensible Markup Language
Focus on	How do data look like? Displaying data	What is data about? Describe the data
Tag Type	Predefined	User Defined
Data Storage	Stored in the Tags	Stored in a separate XML file
Case Sensitive	No	Yes
Tag Nature	Not all are close	Must be close

Conclusion

We used the HTML file extension.html and the XML file extension.xml. HTML and XML are both markup languages that allow us to mark up text in a way that makes it easier for computers to read. They are both used to store information in plain-text files.

Thanks for reading this article. I hope this helped you to grasp the topic of the difference between HTML and XML.

FAQs

Q. Can I use HTML and XML together?

A. Yes, you can use HTML and XML together in certain scenarios. For instance, you might embed XML data within an HTML document, and then use JavaScript or server-side scripts to extract and manipulate that data.

Q. Is XML replacing HTML?

A. No, XML is not meant to replace HTML. They serve different purposes. HTML is for presenting content in a human-readable format on the web, while XML is for describing and structuring data that can be used by various applications.

Q. Which one should I use - HTML or XML?

A. It depends on your use case. If you want to present content on the web, use HTML. If you need to define custom data structures or exchange data between different systems, use XML.

Q. Is HTML5 an XML-based language?

A. HTML5 is not an XML-based language. It is based on SGML (Standard Generalized Markup Language), which is a predecessor to XML. However, HTML5 introduced stricter syntax rules, making it more XML-like, but it is not a true XML language.

Q. Can XML be used for website development like HTML?

A. While XML can be used for certain aspects of website development, it is not commonly used for rendering web pages like HTML. HTML is specifically designed for web page presentation and user interaction, while XML is primarily used for defining data structures and exchanging information between systems. HTML is a better choice for creating web pages, whereas XML is more suitable for data representation and communication.

Q. Can I convert HTML to XML and vice versa?

A. Yes, you can convert HTML to XML and vice versa, although the process may not always be straightforward. There are tools available that can assist with the conversion, but keep in mind that the resulting XML may not fully capture the original semantics or structure of the HTML document, as HTML and XML serve different purposes.

Q. What is the relationship between XHTML and XML?

A. XHTML (Extensible HyperText Markup Language) is a stricter and cleaner version of HTML, conforming to XML syntax rules. It was introduced to bridge the gap between HTML and XML and bring the benefits of XML, such as extensibility and adherence to XML rules, to HTML. XHTML documents are also well-formed XML documents, which means they can be parsed by XML processors.

Q. Can I use XML without a DTD or XML Schema?

A. Yes, you can use XML without a DTD (Document Type Definition) or XML Schema. However, using a DTD or XML Schema provides significant advantages. They define the rules and structure for the XML document, allowing validation and ensuring that the document conforms to the expected format. Without a DTD or Schema, the XML document is considered "unvalidated," making it harder to ensure its correctness and integrity when exchanged between different systems.