Subscribe to Events

Task: Subscribe to Events


Aim: One way of interacting with the ENVISION platform as an end user is offered by the Subscription Portlet. The Portlet allows subscriptions to natural events and disasters, handled by a specific platform, within a desired region. When an event happens or is about to happen, users subscribed to the event get a notification via e-mail.


  1. The Semantic Notification Broker (Web service handling the semantic matchmaking between subscribers and triggered events) has to run under
  2. The page to which the Subscription Portlet will be added has to contain the ENVISION Map Viewer or the ENVISION EventVisualizer to define the desired region.

Brief description:

The Notification Module enables notifications about the occurrence of events via e-mail. The module comprises the SubscriptionPortlet, the Semantic Notification Broker (SNB), and Event Processing Service (EPS). The Portlet acts as an UI to the infrastructure that can be easily integrated into the ENVISION platform. Editors of a platform have the opportunity to configure the Subscription Portlet regarding provided topics. The SNB serves as a backend and stores all the user-generated data and is responsible for the notifications via e-mail based on intelligent inference tasks. Via a message channel (EventBUS) the SNB retrieves occurring events. Events are identified by the EPS. When an event is detected, the EPS pushes the corresponding message into the EventBUS.

By the use of semantic Web technologies, complex functions and processes are hidden, reducing the effort and increasing the usability of the Notification Module. However, at least one configuration is required after adding the Portlet to a Portal Page [1].

When the Portlet is configured and events are enabled, end users are now able to subscribe to these events. The following steps describe the subscription procedure.

  1. The user opens the Subscription Window by clicking the “Subscribe” button.
  2. The Subscription Window consists of four tabs. The first tab explains the subscription procedure again.
  3. A specific region can be selected by using the MapViewer or EventVisualizer. For simplification, no extra tools have to be used for the specification of the desired area. Users only have to zoom into their place of interest.
  4. The second tab provides a selection of the kind of notification. Within the ENVISION project only notifications via e-mail are enabled.
  5. Tab three offers event selection. The “Add Event…” button directs users to a new window displaying all events available for subscription. The “plus” button selects an event.
  6. The e-mail address has to be entered in the last tab. When the e-mail address has a valid syntax the subscription process can be finished by clicking the “Subscribe” button.

Concrete example: The Subscription Portlet can be tested by going through the following steps.

  1. Go to the ENVISION platform deployed at
  2. Log in in with username and password envision.
  3. Click on the “Subscribe to Events” tab.
  4. Click on the “Subscribe” button on the left side.
  5. Zoom in the map to the region of interest, e.g. Romania.
  6. In the “Notification Properties” menu, select the kind of notification (only email is supported in this version).
  7. In the tab “Selection of Events”, click on “Add Event…”, and then click on the (+) button next to Flood. Close the “Add Event” window.
  8. In the “Subscription” tab, add your email and click on “Subscribe”.

12. Subscribe to Events

[1]An installation and configuration guide can be found here.

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