Web Service Orchestration enables web services to be strung together in predefined patterns and executed via ‘orchestration scripts’. These scripts will often map to business processes or inter/intra-company workflow. Often the scripts describe the interaction between applications by identifying messages, branching logic and invocation sequences.

The piece of software that runs a WSO script is called an orchestration engine. In this setting, the WSO engine acts as a centralized authority to coordinate interaction between services.

BPEL4WS and WSCI are examples of web service orchestration languages.