IBM BPM, V8.0.1, All platforms > Authoring services in Integration Designer > Advanced development topics > Assuring Quality of Service > Quality of service qualifier reference

Event sequencing qualifier

The event sequencing qualifier ensures that events are processed in order and that one event is completely processed before the next one is processed.

The event sequencing qualifier places a control on the order in which the runtime environment processes events. You specify a group of one or more operations and a key. When two or more events are received that invoke any of those operations that have the same key, the event sequencing qualifier ensures that they are processed in the order they are received. Without a keyed qualifier, the multithread runtime environment does not necessarily process events in the order that they are received.

Location: You can only apply event sequencing qualifiers to interface operations.

Settings: The event sequencing qualifier requires values for these settings:

• Group name - The group identifies which operations will participate in a particular sequence.

  For example, operations involved in reserving a hotel room might be in one group and operations involved in renting out the convention hall in another group, assuming operations on hotel rooms are completely independent from operations on convention halls.

• Key definition - The key is a set of XPath expressions that identify the object being manipulated. The keys for the first set of operations are the room numbers, such as 201 (second floor, room 01). The keys for the second set of operations might be room names like "Main ball room" and "West projection room." Once you have identified those properties, you need to add an event sequencing qualifier on all the operations, specifying that key.
• Order - The sequence in which the XPath expressions appear in the key may matter. For room numbers, the value showing the floor must always appear first.

Application: Event sequencing is supported only for components that are invoked using the SCA asynchronous invocation style. Invocations have parameters, which are business objects or simple types. The key is a combination of one or more business object attributes. You can set the event sequencing qualifier after you develop the business logic; it is independent of the implementation. See the related tasks at the end of this topic for a link to information about using event sequencing.

Quality of service qualifier reference

Related tasks:
Processing events in a sequence