Gav's Blog

I haven’t blogged about Sahana for a long time, and I’ve got plenty to write. So much that I can’t decide where to start, so I’m going to pick a nice small piece to start with.

The Concept

Last year, I was involved in a project in New Zealand to produce an investigative report on Public Alerting Systems with the New Zealand Centre for Advanced Engineering. This report will hopefully soon go public, and I’ll provide a link when it does.

This report was looking at the different technological solutions for getting alerts out to people in as timely a manner as possible. At one point in the search for different systems, we started discussing means of injecting HTML in web pages via an ISP, so that a public alert could be sent out to anyone on the Internet. I’ll talk about this and other options later. Let me get to the point of this post.

After starting at the HTML injection idea, and progressing through a few others, I reached a kind of natural conclusion that a more suitable means of alerting users via a web browser would be a browser plugin that can subscribe to Common Alerting Protocol (CAP) feeds, and when a relevant alert comes in via CAP, this is displayed to the user in their browser using the XUL:notificationbox at the top of the webpage.

Draft Requirements

Anyway, a possible idea for a Google Summer of Code 2009 project is that of constructing a browser plugin for Firefox that implements this alerting capability, and expanding Sahana to support full publishing of CAP alerts. Here are some features it could/should support.

Firefox Plugin

• Bundle publicly available CAP feeds (ideally listed in a nice Country/State taxonomy – this will make it easy to discover and utilise existing CAP services.
• Allow users to optionally register location in some manner, so as the plugin can identify relevant alerts (by location) and give them higher status than say remote alerts. Users should be able to register multiple locations – whether it has home & work, or multiple cities. Privacy is of course king and this information must be protected.
• Provide a means of adding additional user provided CAP feeds to the plugin.
• Provide the ability to open the alert in a new tab and format in a human-readable manner, including niceties such as embedding Google Maps to show geospatial information and links back to the source website of the alert for verification.
• Implement means of verifying messages that are digital signed, and decrypting encrypted messages.

Sahana

• Implement a CAP feed in Sahana so that Sahana can act as both a producer (in terms of creating a CAP message) and a publisher (in terms of making it available via a CAP RSS/Atom feed).
• Implement a CAP proxy or similar, so that say all users of a Sahana server can obtain CAP alerts directly from the Sahana server – rather than going to an external website. This may be useful for distribution of alerts within an organisation or centre without having every client browser connecting to an external server.

What would be very nice, but may be beyond the capabilities of Sahana servers currently, is making the CAP service on a Sahana server easily discoverable on a LAN via zero-conf services such as Bonjour.

Draft Outcomes for Assessment

The outcome of such a project would be to produce a working solution whereby a Firefox Browser plugin is capable of working with public CAP alerts and that CAP within Sahana is capable of fully acting as a CAP server via RSS/Atom feeds to the CAP alerting plugin.

Compulsory

• Implement the specified requirements
• The browser plugin works as expected with publicly available CAP feeds.
• The browser plugin works as expected against the Sahana demo server. (Yes, this means that your modifications to CAP on SahanaPHP need to be implemented).

Optional

• Implement the Sahana CAP server in SahanaPY
• Provide one or more standalone CAP clients for a mobile platform e.g. Google Android, Apple iPhone/iPod Touch etc
• Write an Internet Explorer plugin with similar functionality – it is important that this functionality is also provided for IE given its widespread usage and deployment.

Whilst the plug-in can and should operate completely independently of Sahana, it should also be designed to work well with Sahana servers (e.g. SahanaPHP and SahanaPY).

Anyway, this is just an idea I wanted to float and get out in the community for discussion. I’d welcome any further comment or ideas to build upon this!