It uses the Simple Object Access Protocol, a protocol for a common XML (Extensible Markup Language) messaging format for Internet applications.

CNN: Technology - Gates offers developers glimpse of Next Generation Windows

Workday's software makes prodigious use of the Web's extensible markup language, or xml, which facilitates sharing of documents or data among applications.

FORBES: Magazine Article

Ajax (geek shorthand for asynchronous JavaScript and XML, which itself is short for extensible markup language) preloads Web content so users can change text, crop and move pictures and add multicolored borders without waiting for a page reload.

FORBES: Zazzle It