Sensors are used to declare interest in specific events throughout the life cycle of a BPEL process instance. In a business process, that can be the activation and completion of a specific activity or the modification of a variable value in the business process.

When a sensor is triggered, a specific sensor value is created. For example, if a sensor declares interest in the completion of a BPEL scope, the sensor value consists of the name of the BPEL scope and a time stamp value of when the activity was completed. If a sensor value declares interest in a BPEL process variable, then the sensor value consists of the following:

• The value of the variable at the moment it was modified

• A time stamp when the variable was modified

• The activity name and type that modified the BPEL variable

The data format for sensor values is normalized and well-defined using XML schema.

A sensor action is an instruction on how to process sensor values. When a sensor is triggered by Oracle BPEL Process Manager, a new sensor value for that sensor is created. After that, all the sensor actions associated with that sensor are performed. A sensor action typically persists the sensor value in a database or sends the normalized sensor value data to a JMS queue or topic. For integration with Oracle BAM, the sensor value can be sent to the Oracle BAM adapter.

You can define the following types of sensors, either through Oracle JDeveloper or manually by providing sensor configuration files.

• Activity sensors

  Activity sensors monitor the execution of activities within a BPEL process. For example, they can monitor the execution time of an invoke activity or how long it takes to complete a scope. Along with the activity sensor, you can also monitor variables of the activity.

• Variable sensors

  Variable sensors are used to monitor variables (or parts of a variable) of a BPEL process. For example, variable sensors can monitor the input and output data of a BPEL process.

• Fault sensors

  Fault sensors are used to monitor BPEL faults.

You typically add or edit sensors as part of the BPEL modeling of activities, faults, and variables.

These sensors are exposed through the following public SQL views:

• BPEL_ACTIVITY_SENSOR_VALUES

• BPEL_FAULT_SENSOR_VALUES

• BPEL_VARIABLE_SENSOR_VALUES

These views can be joined with the BPEL_PROCESS_INSTANCES view to associate the sensor value with the BPEL process instance that created the sensor values. For more information, see Understanding Sensor Public Views and the Sensor Actions XSD.

When you model sensors in Oracle JDeveloper, two new files are created as part of the BPEL process archive:

• bpel_process_name_sensor.xml

  Contains the sensor definitions of a BPEL process

• bpel_process_name_sensorAction.xml

  Contains the sensor action definitions of a BPEL process

For information about how these files are created, see How to Configure Activity, Variable, and Fault Sensors and How to Configure Sensor Actions.

After you define sensors for a BPEL process, you must configure sensor actions to publish the sensor data to a specified destination. If no sensor action is defined for a sensor, then nothing happens at runtime.

The following information is required for a sensor action:

• Name

• Publish type

  The publish type specifies the destination in which the sensor data must be presented. You can publish sensor data to the following destination types.

  • Database

    Publishes the sensor data to the reports schema in the database. The sensor data can then be queried using SQL.

  • JMS queue

    Publishes the sensor data to a JMS queue. The XML data is posted in accordance with the Sensor.xsd file. This file is included with Oracle JDeveloper in the following directory:

    /soa/integration/seed/soa/shared/bpel/Sensor.xsd
    

    The Sensor.xsd file is also included in the following directory:

    /soa/integration/jdeveloper/seed/soa/shared/bpel/Sensor.xsd
    

  • JMS topic

    Publishes the sensor data to a JMS topic. The XML data is posted in accordance with the same Sensor.xsd file used with JMS queues.

  • Custom

    Publishes the data to a custom Java class.

  • JMS Adapter

    Uses the JMS adapter to publish to remote queues or topics and a variety of different JMS providers. The JMS queue and JMS topic publish types only publish to local JMS destinations.

• List of sensors

  The sensors for a sensor action.