Version 8 (modified by Nuwan Waidyanatha, 11 years ago) ( diff )


BluePrint: CAPBroker

Current Status



Common Alerting Protocol defines a data format for sending out alerts (and re-relaying) over various broadcasting channels. This project aims to implement core CAP features into Eden and provide usable UI elements for generating CAP alerts manually.

A Sahana Eden instance that has subscribed to available broadcasters will (e.g. USGS or GDACS CAP feeds) then recieve the alert. Thereafter, an authorized Sahana Eden user can amend the content and relay that message to recipients registered in the Sahana Eden instance. They could be human subscribers or other systems linked to Sahana Eden, thus alerting them of an imminent tsunami, for example.

Similarly, a manually recorded landslide can be broadcast by an Eden server which will be sent out to the traffic control system, for example, which will allow it to automatically determine a custom traffic routing.


User story:

  • A an emergency response agency learns of an imminent disaster say a Tsunami, and the following are the steps they take up:
  • In Eden's CAP interface the operator chooses the CAP Profile for their region
  • He then chooses a CAP Template specific for Tsunami
  • He then edits the blanked out fields in the template (for example, area description, severity) and also sets a few flags (these are provided as per the CAP 1.2 specification)
  • He will then optionally attach files (eg. containing pre-decided evacuation instructions etc) and also add a few more language templates and edit them
  • He then sends the CAP Alert as a "Public" alert which everyone subscribed or added in the contacts is notified about
  • Since CAP is an XML standard it can be easily picked up by automated systems and required actions maybe performed (eg. Sirens)

Sahana Agasti has a CAP broker implementation


  • Functional:
    • CAP Profiles and CAP Templates: Data model and user interface assisting easy and correct implementation of CAP profiles and create/edit of CAP templates
    • CAP Editing: Data model and user interface for creation of CAP alerts compliant with the EDXL-CAP 1.2 standard.
    • CAP subscriber: data model and GUIs to manage intended users and groups when disseminating alerts via SMS and Email. (we can use s3msg module here)
  • Interoperability:
    • CAP Broadcasting: Use XSL and XSLT to generate text suitable for distribution. Generate broadcast events, broadcast media can be added by hooking up to these events generated in the system: tap in to s3msg module
    • CAP Reception: Expose a PuSH end point and allow Eden instances to subscribe to each other. Handling cancellation and update alerts gracefully.
    • Import and Export facility for CAP and CAP Profiles: Enable importing of CAP Alerts from XML files with CAP Alert elements. Allow Exporting. Use the Survey module as a reference here. Also these should be implemented inside the s3export module.


Actor Use-case Description
CAP profile implementer Implement CAP profile CAP Profile defines a class of CAP alerts which may provide a structure to the CAP alert and speed up the creation of CAP Alerts and templates, for example a Profile may specify a region, a set of languages and generic templates in each language. This can be used during CAP alert creation for centering the map for example and for fast creation of alert messages
CAP template implementer Implements CAP templates CAP templates are Abstract CAP alerts with blanks that need to can be filled really fast in case of an imminent disaster to produce a CAP alert, for example a Tsunami CAP template might be of help in a coastal area, hence an implementer will create the same
CAP message editor Send a CAP alert a message editor can pick a CAP template and fill the blanks in it to send out a CAP alert (user story in description)
CAP alert subscriber Subscribes to CAP Alerts when a CAP alert is created and the subscriber is in the audience, a notification will be issued via modes prescribed by the subscriber


  • The Models: The table definitions go are in modules/s3db/ Place some functions which will help in the creation, sending and receiving of CAP XML files in s3msg module where it might best fit.
  • The GUI
    • index: A map and a table of alerts sortable by the various fields of an alert. Clicking on a row on the table centers the map to the <Area> associated with the alert.
    • profiles:
      • index: View a listing of templates (We should ship some country-specific profiles by default in Eden since this is recommended)
      • edit & create: Editing / creating a profile. This should allow for specification of constraints for each field of the cap message.
    • templates:
      • index: View a listing of all templates grouped by their pertinent profiles.
      • edit & create: Allow users to create templates: This will allow for creating multiple <info> elements with placeholders for canned inputs such as [AREA] [SEVERITY] etc.which will then be substituted to produce text consumable via various media like SMS and IVR
    • create alert: A map with ability for easy input of polygons and circles, A drop-down for picking profiles and templates to use. A way to specify recipients for restricted alerts.
    • Reference and mockups:




Common Alerting Protocol:

Originating CAP alerts is one need, receiving them and using them to actuate alerting systems, be they SMS drivers or sirens or whatever is another. Another is a message broker that can interoperate with the commercial boxes. Authentication systems are also a factor, especially where cross-jurisdictional reciprocity is required

Ideally the CAP XML should be signed end-to-end, especially in a federated system where there's more than one authority running servers/aggregators. Our current implementations sign the alerts at the originating server, so they're at least traceable to the source server but not necessarily the individual operator. Current servers check integrity when they get a message from another server, but there isn't a regional PKI.

Wireframe (ported to eden)

  • The wireframe built using Python and Eden frameworks. The code is here. Anyone can use this as the basis to continue the CAP Broker developments.
  • This ticket contains some of the screen shots and initial GUI layouts with some descriptions.


Attachments (6)

Download all attachments as: .zip

Note: See TracWiki for help on using the wiki.