What is XML AND What is Used For?

XML, short for Extensible Markup Language, is a straightforward, text-based format designed to represent various forms of structured information. Its applications range from documents, data, and configurations to books, transactions, invoices, and much more. XML originated from an earlier standard format known as SGML (ISO 8879) and was specifically developed to enhance its suitability for utilization on the World Wide Web.

What is XML Used For?

XML stands as a highly prevalent format employed for the sharing of structured information in various contexts. It serves as a means of communication between programs, individuals, computers, and the convergence of these entities, whether it be on a local scale or across networks. The versatility of XML enables seamless exchange and transmission of structured data in a myriad of scenarios.

Certainly! Here's an example of XML code representing a simple address book:

<addressBook>
  <contact>
    <name>John Doe</name>
    <email>john.doe@example.com</email>
    <phone>123-456-7890</phone>
  </contact>
  <contact>
    <name>Jane Smith</name>
    <email>jane.smith@example.com</email>
    <phone>987-654-3210</phone>
  </contact>
</addressBook>

In this example, we have an <addressBook> element as the root element. Inside the <addressBook> , we have two <contact> elements representing individual contacts. Each <contact> element contains nested elements for <name> , <email> , and <phone> , representing the name, email address, and phone number of each contact, respectively.

Note

Please note that this is a simplified example, and in real-world scenarios, XML can have more complex structures with additional elements, attributes, and namespaces, depending on the specific requirements of the data being represented.

If you are familiar with HTML, you'll notice that XML bears a striking resemblance. However, XML enforces stricter syntax rules compared to HTML. XML tools won't process files that contain errors; instead, they will provide error messages, allowing you to rectify them. Consequently, nearly all XML documents can be reliably processed by computer software.

Here are the main differences from HTML:

Closure of Elements: All elements in XML must be closed or marked as empty. Empty elements can be closed in the normal form, such as <happiness></happiness>, or using a special short-form syntax, like <happiness />.

Quoting Attribute Values: In HTML, attribute values only need to be quoted under certain circumstances, such as when they contain spaces or characters not allowed in a name. However, in XML, attribute values must always be quoted. For example: <happiness type="joy" />.

Built-in Element Names: HTML has a predefined set of element names along with their attributes. In XML, there are no predefined names, although names starting with "XML" have special meanings.

Furthermore, in HTML, there is a predefined list of character names like &eacute; for é. However, XML does not have such built-in character names. Instead, XML provides only five built-in character entities: &lt;, &gt;, &amp;, &quot;, and &apos;, representing <, >, &, ", and ', respectively. In XML, you can define your entities using a Document Type Definition (DTD), or you can directly use any Unicode character.

Additionally, HTML allows the use of numeric character references, such as &#38; for &. While HTML primarily uses decimal numbers for these references, XML supports both decimal and hexadecimal references. For example, in XML, you can use &#x26; to represent &.

These distinctions highlight the stricter nature of XML compared to HTML, ensuring more reliable processing by software tools and offering greater flexibility in handling character entities and references.