While JSON has become more popular for web APIs, XML is still widely used in many applications, particularly in enterprise environments, document management, and data interchange where strict validation and complex data structures are required. Here are some current applications of XML:

1. Data Exchange and Interoperability:

• B2B (Business-to-Business) Transactions: XML is a cornerstone of many B2B standards, facilitating the exchange of data between businesses, such as purchase orders, invoices, shipping notices, and product catalogs. Standards like EDIFACT and ebXML rely heavily on XML.

• Web Services:

• SOAP (Simple Object Access Protocol): Although REST with JSON is more common now, SOAP web services, which use XML for message formatting, are still prevalent in enterprise systems. SOAP defines a strict XML-based protocol for exchanging structured information.

• WSDL (Web Services Description Language): WSDL files, which describe the operations and data types of a web service, are written in XML.

• Data Integration: XML serves as a common format for integrating data from disparate systems, even if those systems use different internal data representations. This is crucial in large organizations with legacy systems.

• Data Feeds: RSS (Really Simple Syndication) and Atom feeds, used for distributing news headlines, blog posts, and other updates, are XML-based formats.

2. Configuration Files:

• Application Configuration: Many applications, especially in Java and .NET environments, use XML files to store configuration settings, such as database connection strings, logging parameters, and application behavior. Examples include:

• Java's web.xml (for web applications) and various Spring framework configuration files.

• .NET's app.config and web.config files.

• Operating System Configuration: Some operating system components use XML for configuration.

• Build Tools: Build tools like Apache Ant and Maven use XML files (build.xml and pom.xml, respectively) to define project structure, dependencies, and build processes.

3. Document Storage and Management:

• DocBook: A widely used XML schema for technical documentation, particularly for books and articles about computer hardware and software.

• TEI (Text Encoding Initiative): An XML schema for encoding literary and linguistic texts, used in digital humanities and scholarly publishing.

• Microsoft Office Open XML (OOXML): The file formats for Microsoft Office documents (.docx, .xlsx, .pptx) are based on XML. These files are actually ZIP archives containing XML files that define the document's structure, content, and formatting.

• OpenDocument Format (ODF): An open standard for office documents (used by LibreOffice, OpenOffice.org, and others) that is also based on XML.

• Content Management Systems (CMS): Some CMSs use XML to store and manage content, either directly or as an intermediate format.

4. Graphics and Vector Images:

• SVG (Scalable Vector Graphics): An XML-based format for describing two-dimensional vector graphics. SVG images can be scaled without loss of quality and are often used for logos, icons, and illustrations on the web. SVG files can be embedded directly into HTML.

• XAML (Extensible Application Markup Language): Used in Microsoft's .NET framework for defining user interfaces in Windows Presentation Foundation (WPF) and Universal Windows Platform (UWP) applications.

5. Specific Industry Standards:

• Financial Services:

• FIX (Financial Information eXchange): A protocol for electronic trading. While FIX originally used a tag-value format, there is also an XML-based version called FIXML.

• FpML (Financial products Markup Language): An XML standard for describing over-the-counter (OTC) derivative transactions.

• XBRL (eXtensible Business Reporting Language): An XML-based standard for financial reporting.

• Healthcare:

• HL7 (Health Level Seven): A set of standards for exchanging healthcare information. While HL7 v2 uses a custom delimited format, HL7 v3 and FHIR (Fast Healthcare Interoperability Resources) support XML representations.

• CDA (Clinical Document Architecture): An XML-based standard for clinical documents.

• Publishing:

• MathML (Mathematical Markup Language): An XML application for describing mathematical notation. Used in scientific and technical documents.

• JATS (Journal Article Tag Suite): An XML format for archiving and exchanging journal articles.

• Geospatial Data:

• GML (Geography Markup Language): An XML grammar for expressing geographical features.

• KML (Keyhole Markup Language): Used to display geographic data in applications like Google Earth.

6. Databases:

• Native XML Databases: Databases specifically designed to store and query XML data (e.g., BaseX, eXist-db).

• XML Support in Relational Databases: Most major relational database systems (e.g., Oracle, SQL Server, PostgreSQL, MySQL) offer features for storing, querying, and manipulating XML data within the database.

7. Other Applications:

• Robotics: The Robot Operating System (ROS) uses XML in many configuration and data description files.

• Music: MusicXML is a standard open format for exchanging digital sheet music.

• Android app development: Layouts and resources are defined in XML.

In summary, although JSON has gained prominence in web development, XML remains a vital technology for various applications that require structured data representation, robust validation, and interoperability, especially in enterprise and industry-specific contexts. Its extensibility and well-defined standards make it a reliable choice for complex data management and exchange.