Serving Illinois, Maryland, and the District of Columbia, BlueStar buys electricity on the broader market and resells it to residential and business customers, some of whom have complicated needs. The trick, as CTO Tom Keen explains, is to buy smart and schedule delivery in an optimal way. That requires managing the flow of information—and purchase and billing transactions—across multiple parties: power generators, transmission operators, local distribution companies, and last but not least, BlueStar customers.

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"We basically help customers define contracts that maximize their energy dollar," Keen says. "Some customers only want to use pure green energy. Some would like to run on brown energy and purchase what are called carbon offsets. We can do that as well. There's just a tremendous blend of how you buy power, plus how much risk you want to take on. So we can do fixed options. It's an extremely complex configuration."

Here, the challenge isn't just to design complex products, it's to bill them. Not only does BlueStar have to track each customer's hourly electricity usage, but it must also reconcile that usage with the cost of the power for each specific hour—a task made more difficult by the myriad methods (EDI, XML, FTP, Excel, CSV, and so on) local distributors employ to provide that information.

To automate customer provisioning and payments to trading partners, BlueStar brought together a heady mix of open source software, including an ESB, JMS message broker, a business rule management system, and BPM. A b-to-b gateway integrates all of BlueStar's partners and translates all of the different feeds and data formats for BlueStar's back-end systems. The loosely coupled approach insulates BlueStar's accounting application and other systems against all the complexity of the outside world.

"The b-to-b gateway is a distributed implementation of an ESB," says Guillermo Tantachuco, director of enterprise architecture at BlueStar. "We don't have a huge monolithic server that handles all this. These are a bunch of services scattered across our network that are pretty resilient. If one instance dies, another one is ready to take over."