6.6. XBlocks, Events, and Grading

Events are emitted by the server or the browser to capture information about interactions with the courseware.

In most cases, your XBlock must emit events.

For example, assigning a grade is a common event.

6.6.1. When an XBlock Should Emit Events

Analysis of events can provide insight about how learners use the XBlock. Using event data, analysts should be able to reconstruct the state of the XBlock at any point in time.

Your XBlock should emit an event whenever a significant state change occurs, and when a grade for the learner’s interaction is assigned. For example, when a learner submits an answer or otherwise interacts with your XBlock, an event should record that action.

To assign grades from your XBlock, it must emit a grade event.

6.6.2. Publish Events in Handler Methods

You define handler methods to emit events.

In the handler, you use the XBlock runtime interface publish method to emit the event. The runtime.publish method causes the runtime application to save the event data in the application event stream.

The following code shows the runtime.publish method syntax in an XBlock handler.

self.runtime.publish(self, "event_type",
                     { event_dictionary })

Note the following information about the runtime.publish method.

  • The event_type uniquely identifies the event in log files.
  • The event dictionary contains key-value pairs that define the event.

6.6.3. Publish Grade Events

To assign a grade for a learner’s interaction with the XBlock, the XBlock handler method must publish a grade event.

A grade event uses the runtime.publish method with specific arguments.

  • The event type is grade.
  • The event dictionary must contain two entries.
    • value: The learner’s score
    • max_value: The maximum possible score

The current user’s user_id is implicit in the event dictionary.

..The event dictionary can also contain the user_id entry. If user_id is not specified, the current user’s ID is used.

For example, the following handler code emits a grade for the learner that is stored in the submission_result variable in an XBlock with the maximum grade of 1.0.

self.runtime.publish(self, "grade",
                    { value: submission_result
                      max_value: 1.0 })

Typically, the handler method also returns the calculated grade, so that it can be displayed to the learner. has_score Variable

To be graded, in addition to publishing the grade event, the XBlock must also have a has_score variable set to True.

has_score = True