- A common approach, or common language for defining components and interfaces
- Contracts between different components through a common interface definition
- A platform to enable components to work together in a corporate, or even an inter-corporate, environment
- A method to orchestrate components and to foster composition
- Infrastructure layer
- Runtime layer
- Function layer
- Message order cannot be guaranteed, because each message may be processed by any one of the cluster members.
- With only two cluster members fail over is not possible, because each ME has its own datastore assigned and only one ME per cluster member can be active for one SIB. As a result, data of Message Points cannot be transferred from one ME to another.
- The BPC Bus is used by the Business Process Choreographer for executing long running processes. Messages on the BPC Bus are so called navigational messages, which hold status and processing information about the corresponding processes. For example, the transition from one activity to another may lead to a navigational message, if each activity participates in its own transaction. The transactional behavior can only be changed during development time and can neither be viewed nor be changed at runtime.
Setting the optimal transaction boundaries may be considered as one of the key performance aspects for process implementations for different reasons. First, transaction context switches are quite expensive operations in terms of computation time. Second, crossing transactional boundaries leads to a navigational message in the case of long-running processes, which is also more expensive than staying within the same transaction.
- The SCA System Bus is used by the SCA runtime for asynchronous communication between SCA components and SCA modules. The messages flowing through the Bus contain business data (originated from requests between the different SCA artifacts) and are not used for navigational purposes as with messages on the BPC bus.
- The SCA Application Bus is most commonly used for custom destinations of SCA Modules. For example, the JMS Destinations referred to by an JMS Export should refer to Destinations residing on this bus.
- The CEI Bus is used for asynchronous event transmission. The messages on this bus are the events that are picked up by a special MDB to be transferred for further processing to the so called Event Server application.
- The WPRCSDB silo contains configuration and cell wide data of WebSphere Process Server. For example data about some SCA components (Business Rules, Selectors, Relationships) is stored here. Furthermore, the data silo contains the Failed Event data. Because Failed Event information is needed in some cases to restart failed SCA flows, the availability of this data is quite important. This database exists just once per WebSphere Process Server cell.
- The MEDB silo is used by the Messaging Engines running in WebSphere Process Server messaging infrastructure (see the previous section for more details) to persist messaging data: transaction context, message payload and administrative information. Each (active) Messaging Engine needs its own Schema within this database.
- The EVENT silo data silo contains the data of the Common Base Event Infrastructure. If the option to persist all event data is selected it will be placed here.
- The BPEDB silo contains Business Process Choreographer data, amongst other things the template data of processes and human tasks, status information of long running processes, and so forth. This data silo can exist several times in a cell if more than one server or cluster is configured for running Business Processes and/or Human Tasks.