BPEL processes overview
A business process is a set of business-related activities that are invoked to achieve a business goal.
A BPEL process is a business process that is defined in the Web Services Business Process Execution Language, and comprises the following constructs:
- The activities that are the individual steps within the process.
An activity can be one of several different types. Also, an activity
can be categorized as either a basic activity or a structured activity.
- Basic activities are activities that have no structure and do not contain other activities, for example, assign or invoke activities.
- Structured activities are activities that contain other activities, for example, sequence or while activities.
- The partner links, also known as interface partners or reference partners, that specify the interaction with external partners using WSDL interfaces.
- The variables that store the data that is exchanged with the process and passed between activities.
- Correlation sets that are used to correlate multiple service interactions with the same BPEL process instance. Correlation sets are based on application data that is contained in messages that are exchanged with the process.
- Fault handlers that deal with exceptional situations that can occur when a process runs.
- Event handlers that receive and process unsolicited messages in parallel to the normal process execution.
- Compensation handlers that specify the compensation logic for a single activity, a group of activities, or a scope.
For more information on these constructs, refer to the BPEL specification.
Business Process Choreographer also supports the IBM® extensions to the BPEL language, such as:
- Human task activities for human interaction. These inline to-do tasks can be steps in the process that involve a person, for example, completing a form, approving a document, and so on.
- Script activities for running inline Java™ code. The Java code can access all of the variables, correlation properties, partner links, and process and activity contexts.
- Information service activities to directly access WebSphere® Information Server or relational databases.
- Timestamps for process versioning.
- Extensions for manually setting or controlling the transactional boundaries in a BPEL process.
- Timeouts for activities.
- Process templates
A BPEL process template is a process definition that is deployed and installed in the runtime environment. - Process instances
A process instance is the instantiation of a process template. - Lifecycle of BPEL processes
When a BPEL process is initiated, the navigation of a process instance is started, and it begins to interact with its environment. Certain interactions are only possible in particular process states, and these interactions, in turn, influence the state of the process instance. - Dynamic modification of BPEL process instances
Typically, a BPEL process is navigated as defined in the process model. However, sometimes you might need to override the navigation of a process instance at run time, for example, so that you can repair a process instance, or perform only those activities that are appropriate for the current context. - Invocation scenarios for BPEL processes
A BPEL process is a Service Component Architecture (SCA) component implementation. It can expose services to other partners and consume services provided by other partners. A BPEL process can be a service provider that is made available by the Business Process Choreographer APIs, an SCA service provider for other SCA service components, or an SCA client that invokes other SCA service components, including other BPEL processes. - Transactional behavior of BPEL processes
BPEL processes are executed as part of transactions. The navigation of a BPEL process can span multiple transactions in the case of long-running processes, or happen as part of one transaction in the case of microflows. - Fault handling and compensation handling in BPEL processes
A fault is any exceptional condition that can change the normal processing of a BPEL process. A fault can be returned from a service invocation, raised explicitly by the process, or it can be system fault raised by the runtime environment. A well-designed process should consider faults, and handle them whenever possible. Compensation is one way of handling faults.
Parent topic: BPEL processes and human tasks
Related concepts:
