XML (Extensible Markup Language) uses descriptive text-based elements (tags) and attributes to provide context for the content contained in an XML document. In effect, XML is as a language that allows you to define markup languages. An XML schema or DTD (Document Definition Type) provides a set of rules for element and attribute names allowed, attribute value data types, and allowable child elements. XHTML is an example of XML being used to define an application-specific markup language. You will most likely encounter XML when modifying web page configuration files or viewing the exchange of information in web services requests and responses. For more information, see Wikipedia or W3.org. Web Services are defined as software systems that enable machine-to-machine interactions over networks. Typically, a client makes a web service request to a server, and the resulting information is returned to the client in an XML format. Note that the “client” can be one server talking to another server. 2 predominant web services frameworks, SOAP and REST, are used in web site development.