The Canadian Geospatial Data Infrastructure (CGDI) is based on a web service architecture.

A web service is any software that makes itself available over the Internet and uses a standard messaging system. There is no single definition for web services, but most descriptions of web services highlight the following three characteristics:

1. They are discrete applications handling a specific set of tasks;
   
   
2. They are built using XML interfaces, which allow different web services to be combined within an application; and
   
   
3. Data and functionality are separate from the user interface, so users see a seamless application even though data and functionality may come from many different web services.

These discrete units of software are designed to interact with other software, allowing multiple computers to work directly with one another. Web services are based on industry standard protocols that enable them to interoperate across platforms and programming languages: Windows applications can talk with Unix applications. Interoperability is achieved in part by the use of non-proprietary data and messaging systems such as eXtensible Markup Language (XML).

Web service architectures use the Internet as a distributed computing platform (DCP); as a result, distributed computing no longer requires a heavy financial and training investment in technologies. A service can be made web-accessible no matter how it is implemented, or what platform it runs on. Applications can be easily built from services running on multiple platforms in multiple locations.

Did you know? XML is a non-proprietary representation language developed by the World Wide Web Consortium. It allows web developers to create customized tags that organize and deliver content more efficiently. XML is a metalanguage: it contains a set of rules for constructing other markup languages. By allowing people to make up their own tags, it expands the amount and kinds of information that can be provided about the data held in documents. Many developer tools are available for constructing and parsing XML documents.