Everything You Need To Know About XML

Everything You Need To Know About XML

Data is described using XML (Extensible Markup Language). The XML standard is a versatile method for creating information formats and electronically sharing structured data over the public internet and corporate networks.

XML is a markup language based on the Standard Generalized Markup Language (SGML), which is used to define markup languages.

The primary function of XML is to develop data formats that encode information for documentation, database records, transactions, and a variety of other types of data. You can use XML data to generate various content types by constructing dissimilar types of content based on the XML data, such as web, print, and mobile content.

Like Hypertext Markup Language (HTML), XML documents are stored as American Standard Code for Information Interchange (ASCII) files and can be edited with any text editor.


What Is The Purpose Of XML?

According to the World Wide Web Consortium (W3C), the web’s standards body, the primary function of XML is to provide a “simple text-based format for representing structured information,” including for the following:

  • underlying data formats for applications such as Microsoft Office;
  • technical documentation;
  • application software configuration options;
  • books;
  • transactions; and
  • invoices.

XML allows for the exchange of structured information between and among the following:

  • programs and programs;
  • programs and people; and
  • locally and across networks.

The World Wide Web Consortium (W3C) defines the XML standard and recommends its use for web content. While XML and HTML are both based on the SGML platform, the W3C has also defined the XHTML and XHTLM5 document formats, which mirror the HTML and HTML5 web content standards, respectively.

How Does XML Function?

XML functions by providing a consistent data format. Formatting is strictly enforced in XML; if the formatting is incorrect, programs that process or display the encoded data will return an error.

To be considered well-formed, an XML document must be valid XML code; that is, it must conform to XML syntax and be read and understood by an XML parser. Elements are the building blocks of all XML documents; an element serves as a container for data.

Opening and closing tags mark the beginning and end of an element, with other elements or plain data contained within.

XML functions by delivering properly formatted data that can be processed reliably by programs designed to handle XML inputs. Technical documentation, for example, may include an <warning> element similar to the one shown in the following:

Snippet of XML code:



<emphasis type=”bold”>

          May cause serious injury       


Exercise extreme caution as this procedure could result in serious injury or death if precautions are not taken.  



This data is interpreted and displayed in various ways in this example, depending on the form factor of the technical documentation. This element could be displayed on a webpage as follows:

WARNING: Exercise extreme caution as this procedure could result in serious injury or death if precautions are not taken.

The same XML code is rendered differently on an appliance user interface (UI) or in print. This element could be interpreted to display the text marked as an emphasis differently, such as in red with flashing highlights. The content may be presented in a different font and format when printed.

Presentation is not defined in XML documents, and there are no default XML tags. Most XML applications employ predefined sets of tags that vary according to the XML format. Most users compose their documents using predefined XML formats, but they can also define additional XML elements as needed.

XML Elements 

An XML file’s logical structure requires that all data in the file be encapsulated within an XML element known as the root element or document element. This element identifies the type of data in the file; the root element is <library> in the preceding example.

The root element contains other elements that define the various parts of the XML document; for example, in the preceding example, the root element contains <book> elements, which are composed of the two elements <title> and <author>.

For an XML file to be considered well-formed, You must properly terminate all XML elements. This means that a tag must be properly terminated with an opening and closing tag, such as this paragraph element in a document:


This is an example of a paragraph XML tag.


A tag can also be empty, in which case a forward slash follows it. An empty self-terminating paragraph tag is used in this example to insert an extra space in a document:

<para />

If necessary, XML allows users to define their additional elements. An XML author could add new elements for the publisher, date of publication, International Standard Book Number, and any other pertinent information in the preceding example. You can also define the elements to impose rules on the elements’ contents.

XML Entities 

Predefined entities can be found in XML elements and are used for special reserved XML characters. Custom entities are used to insert a predefined string of characters into an XML file.

The following are the five standard predefined XML entities:

  • &lt; — In XML, the less than symbol (), also known as the open angle bracket, is typically used to indicate the beginning of an XML tag. This entity is used when the open-angle bracket is part of the XML file’s content.
  • &gt; — In XML, the greater than symbol (>), also known as the close angle bracket, is used to indicate the end of an XML tag. This entity is used when the close angle bracket is part of the XML file’s content.
  • &amp; — In XML, the ASCII ampersand symbol (&) is reserved for indicating the beginning of an XML entity. When an ampersand appears within an XML element, this entity is used.
  • &quot; — The ASCII double-quote character (“) is used in XML element tags to identify the element’s optional attribute values. An emphasis> tag, for example, may include options for emphasizing some text, such as bold, italic or underline. When a double quote character appears in the content of an XML element, this entity is used.
  • &apos; — In XML element tags, the ASCII single quote character (‘), also known as an apostrophe, is used to identify element option attributes. An emphasis> tag, for example, may include options for emphasizing some text, such as bold, italic or underline. When a single quote or apostrophe appears in the content of an XML element, this entity is used.

XML entities are denoted by &name, where the entity name starts with an ampersand and ends with a semicolon. Custom entities can be as simple as single characters or as complex as XML elements. Boilerplate language for technical documentation or legal contracts, for example, can be reduced to a single entity. However, when using entities, the XML author must ensure that inserting the entity into an XML file results in well-formed XML data.

Is XML Considered A Programming Language?

Programming languages are made up of instructions used to implement algorithms. In contrast, markup languages format data for processing by programs that run algorithms that interpret marked-up data. XML is a markup language, not a programming language. However, as a markup language, it is used to annotate data with tags that interpret that data.

Because they define different markup language elements and have strict syntax rules for how to compose those elements, markup language tags are considered a type of computer code.

What Exactly Is An XML File?

A plaintext file with the.xml file extension is an XML file. XML files contain Unicode text and can be opened with any application to read text files.

XML files can be edited using a standard text editor or specialized XML editors. An XML editor may include validation tools, such as the ability to:

  • parse XML code and display well-formed XML;
  • flag orphaned text, which is a text that is not enclosed within a tag; and
  • identify improperly formed tags.

An XML file can contain a variety of different types of content. Rich media content, for example, can be incorporated into XML via tags that identify the files containing the rich media content.

How To Read And Open XML Files

An XML file can be opened and edited with any text editor. While text editors may suffice for simple XML file editing, specialized XML editing software is preferred for any extensive XML file writing or editing. With the following features, XML editing programs make it easier to edit XML files:

  • syntax highlighting for tracking complex XML tags;
  • XML parser for validating XML code and displaying parsed data;
  • expanding or collapsing XML tags and nodes;
  • improved interface for editing multiple files at once;
  • graphical user interface for visual display of relationships between XML elements and simplified display of complex XML elements, such as tables; and
  • productivity tools, such as macros, custom elements, and search and replace functions.

The following are some of the most popular XML editing programs:

  • Oxygen XML Editor,
  • XML Notepad,
  • Adobe FrameMaker,
  • MadCap Flare,
  • Quark Author,
  • Liquid XML Studio

XML files are structured in the same way as any other programming code, with headers defining the file’s contents and indentation for nested elements.

What Is The Distinction Between XML And HTML?

While XML and HTML are based on the same underlying SGML foundations, they are not the same and are used in different ways.

The primary distinction between XML and HTML is that XML is used to store data in structured information, whereas HTML is used to represent content. Programs can process XML content reliably because it stores data and enforces strict validation. This is why XML is frequently used to create files that generate HTML content.

Strict validation of XML code means that it will fail when processed for output if the code contains errors. Users can then correct the XML code to be processed successfully. This is critical for XML-based HTML content, but it also makes XML an important format for software configuration files, which must be well-formed to be processed by software.

What Are The Advantages Of Using XML For Documentation?

Because it can specify structural information, XML is widely used for technical documentation. Other programs can then parse this document structure for output.

In HTML, for example, the user can create various types of lists, including numbered lists, but there is no way to tag content as part of a step-by-step procedure explicitly. You can define a procedure tag in XML to represent a list of items as procedure steps, including different elements for required steps, optional steps, and alternate steps.

In the same way, You can tag a string in HTML as one of several different heading levels to indicate a headline or title; a string in XML can be explicitly tagged as a title, subtitle, headline, or subheadline. This allows the user to distinguish between programs that process XML content for different output types.