For the high net worth individuals -- those with more than US$1 million in investments, not including their home -- typically served by private bankers, answering that question is more complicated than simply adding up a few bank and mutual fund account balances and subtracting the mortgage.

Those individuals often have more than a dozen accounts of different types and complexity with a single institution, according to Tom Mitchell, a systems architect with the Private Client Services (PCS) division of Wells Fargo & Co. The PCS division, Wells' private banking group, is one of the largest in the country and manages $195 billion in assets -- almost 40 percent of Wells' total assets -- on behalf of 830,000 clients.

Wells installed the first iteration of its service-oriented architecture (SOA) in the early 1990s to better understand customers' financial data, especially for wealthy individuals with multiple accounts whose data was stored in various databases, data marts and other systems. Nobody called it SOA back then.

"We were pushing text messages -- we called them message units, or MUs -- over TCP/IP before it was cool," Mitchell said.

Wells' system eventually evolved into a modern-services tier based around the WebLogic application server from BEA Systems Inc. It could quickly pull down customer financial data in different application windows. But it could not create a unified, real-time view of multiple accounts. That was something that PCS's bosses wanted to improve service to well-off clients and provide opportunities to sell them relevant products.