What are XML Web Services?
Estimated study time: 14 minutes.
An XML web service is a way for applications running on different platforms to talk to each other over the internet, using XML as the common language for requests and responses.
The Core Idea
Two systems don't need to share a programming language, operating system, or database — as long as both can send and understand XML over standard web protocols like HTTP, they can exchange data.
Typical Building Blocks
- SOAP — a strict, XML-based messaging protocol for web services.
- WSDL — an XML document that describes what a web service offers and how to call it.
- REST (with XML) — a lighter approach where XML is exchanged over standard HTTP verbs.
- UDDI — a (largely historical) directory for discovering available web services.
A Simple Request/Response Flow
Client --request (XML)--> Web Service
Client <--response (XML)-- Web ServiceWhere They're Still Used
XML web services are common in banking, government, healthcare, and other enterprise systems where formal contracts, strict validation, and interoperability with older systems matter more than raw simplicity.
💡 Tip: Even though REST with JSON dominates modern APIs, XML web services (especially SOAP) are still very much alive in large enterprise and government systems — it's a valuable skill to have.