One of the driving factors in IT development is the availability of cheap and efficient network technologies. The Internet is no longer used only as a medium for personal communication. Organizations start utilizing this technology to link existing applications and to create new ones. While traditionally systems were designed to respond to interactive user requests, they are now more and more aiming at autonomous, distributed data processing. Systems are connected and instantly react to changes to improve their functionality and utility (cf. zero latency enterprises). Mobile systems and other volatile configurations demand reactions to continuous changes; finance applications must be notified of price fluctuations; supply chain management must observe stock level changes; and information retrieval applications must forward new content (Banavar, Chandra, Strom, & Sturman, 1999; Gray, 2004).