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Based on the definition of the actual behavior required by a business process, it can be design in two ways using WS-BPEL: abstract and executable. Abstract processes are intended to hide some operational details of the process. As a result, they do not include executable details like process flows. Executable business processes are used to model the actual implementation of the business process.
An abstract process is denoted under the "http://docs.oasis-open.org/wsbpel/2.0/process/abstract" namespace and an executable process is denoted under the "http://docs.oasis-open.org/wsbpel/2.0/process/executable". Additionally, there are syntactical differences between an abstract and an executable BPEL process.
Asynchronous and Synchronous Communication
BPEL processes can also be categorized based on how it invokes an operation of a partner service: synchronous and asynchronous. It is not possible to use both methods when invoking a partner service's operation, as it is dependent on the type of the partner service operation also.
Asynchronous transmission - Assume a BPEL process invokes a partner service. After the invokation of the partner process, the BPEL process continues to carry on with its execution process while that partner service completes performing its operation. The BPEL process then receives a response from the partner service, when the partner service is completed.
Synchronous transmission - Assume a BPEL process invokes a partner service. The BPEL process then waits for the partner service's operation to be completed, and responded. After receiving this completion response from the partner service, the BPEL process continues to carry on its execution flow. This transmission is not applicable to the In-Only operations defined in the WSDL of the partner service.
Usually asynchronous services are used for long-lasting operations and synchronous services for operations that return a result in a relatively short time. Typically, when asynchronous Web services are used, the BPEL process is asynchronous.