What is any piece of software available over the Internet that uses a standardized XML messaging system?

A web service is a specific type of software application that is designed to support interoperable machine-to-machine interaction over a network. It utilizes a standardized XML messaging system, which allows different applications to communicate with each other regardless of the platforms they're built on. This makes web services particularly valuable in the context of the internet, where applications often reside on different servers and may use different technology stacks.

Web services enable the seamless integration of systems, facilitate data exchange, and allow for the execution of remote procedures via protocols like SOAP (Simple Object Access Protocol) and REST (Representational State Transfer). By adhering to a common format like XML, web services ensure that the data sent and received can be understood by any systems involved in the communication.

In contrast, other options refer to different concepts. An API typically refers to a broader concept that defines the methods and formats by which different software components can communicate, but it does not specifically imply the use of an XML messaging system. Microservices architecture focuses on breaking down applications into smaller, independently deployable services, which may or may not utilize a web service. Cloud services are a broad category of services offered over the internet and may include infrastructure as a service, platform as a service, and more, but they do not inherently