A method and system for defining an interface of a service in a service-oriented architecture environment. Definitions of atomic tasks of a request or response operation included in a service are received. Unique identifiers corresponding to the atomic tasks are assigned. A sequence map required to implement the service is received. The sequence map is populated with a sequence of the assigned unique identifiers corresponding to a sequence of the atomic tasks of the operation. At runtime, an interface of the service is automatically and dynamically generated to define the service by reading the sequence of unique identifiers in the populated sequence map and assembling the sequence of the atomic tasks based on the read sequence of unique identifiers.