Enterprise service buses may be synonymous with services orchestration and related capabilities in an SOA. But there is another approach to SOA -- resource-oriented architecture -- that does not rely on the centralized bus but focuses on Web-style integration.

Presenting at TheServerSide Java Symposium in Las Vegas Wednesday evening and interviewed afterward, Brian Sletten, a partner at solutions integrator Zepheira, explained the ESB alternative. While not dead-set against ESBs, Sletten does not always believe they are always necessary.

"My concern about ESBs is people are being sold things they don't necessarily need," he said.

ESBs do provide capabilities such as services registration and discovery, message-handling, standard transformations, process orchestration, and choreography, Sletten pointed out. But there are issues such as a lack of standards.

The Web, meanwhile, has no central authority and no ESB, and it thrives, he said. With resource-oriented architecture, a pipeline can be defined in a non-centralized form and republished as a service, but without exposing back-end details, said Sletten.

With resource-oriented architecture, a URI is used as a common naming scheme. Semantic Web technologies such as Resource Description Framework also can be used.

"It's turning things into nameable information resources, whether it's data, documents, or services and we can do the orchestration by defining higher orders, higher levels of abstraction," he said.

"I like the fact that it allows us to do the orchestration either in a central form or a non-central form whereas an ESB requires you to basically express your pipelines and orchestration on the bus," Sletten said.

Sletten said his company has been setting up resource-oriented architectures at clients in spaces such as the intelligence and financial services communities.