Dealing with legacy systems is like one of those word games, where you have to get from SOUP to SOAP by changing one letter at a time.
SOUP represents legacy. SOAP represents fully compliant service-orientation.
SOA allows for a progressive decoupling of legacy systems - from SOAPY SOUP (legacy systems with some service interfaces) to SOUPY SOAP (service-based architecture with some outstanding legacy areas).
CBDi best practice report - http://www.cbdiforum.com/secure/interact/2003-11/comp_based_srv_eng.php3
CBDi commentary - http://www.cbdiforum.com/public/news/index.php3?id=1341