Unified Communication Systems
http://www.acm.org/crossroads/xrds8-1/ucs.html

Andrews, Christopher R.
ACM Crossroads
2001

Abstract:

Unified messaging and person-to-person communications over heterogeneous networks are relatively new applications. Many commercial messaging systems, such as Onebox.com and Ericsson's Unified Messenger, have already begun their journey in this direction. There is much room for growth, however, and many other systems will soon need the capabilities described above just to stay competitive in the market.