Digital Earth Weblog

Many government agencies have a need to advise other agencies, and the general public, of natural and man-made events. Those events might be weather warnings, agricultural emergencies, traffic incidents, bushfire updates, or many other things. Those events all occur at a location, so there is also a spatial component.

Notification of an event, or an update on an ongoing event, is news to someone who is interested in that event. Imagine a web of network connections between multiple agencies, created using common Web technologies, and across those connections flow news items encoded in a simple machine readable format.

Each information source in the web is a “news feed”. Effectively, by publishing a news feed an agency allows it to be “syndicated”. Other agencies can republish news item via their internal systems, and integrate the data into their workflows.

The most commonly used format for news feeds is RSS, and the latest standard in that area is the Atom Syndication Format. Add in some GeoRSS to provide spatial information, and you have an ideal combination to transfer event details between agencies.

Example Scenario

Your national meteorological agency publishes severe weather warnings on their website, via fax, etc. Other agencies, who have operational responsibilities, would like to obtain those severe weather warnings in a machine readable format. That enables them use software applications, and business rules, to process all items in a news feed and take whatever action is required.

For instance, if a severe weather warning were to be issued for a certain location then the appropriate staff could be notified via email or SMS. It could also be published on an internal website, or in an a corporate system, with hyperlinks to any supporting information.

To make this sort of automated processing possible each news item needs:

• Date and time information. i.e. When it was issued, updated, etc.
• Categories so that software applications can decide what is of interest, and to whom.
• The ability to contain arbitrary HTML content, and a mechanism to support custom extensions.
• Links to other related resources.
• A locational reference that is understood by all parties receiving the news feed.

The Atom Syndication Format takes care of the first four. GeoRSS takes care of the fifth. Atom’s category mechanism can also be used to provide a locational reference using named locations or regions (as shown in the example below).

Example Atom Document

Severe weather warnings from the Australian Bureau of Meteorology have been used to create this example because the BoM make a lot of their stuff available on the web. This allowed the inclusion a lot of links to related information in the Atom document (which makes it a more RESTful design).

Download example document (it’s a bit too large to include inline). Open in any text or XML aware editor.

Some good advice is to not create your own custom XML language unless you really have to. You can do a lot with the Atom Syndication Format, and it’s associated Atom Publishing Protocol.

One of the most powerful features of the Atom Syndication Format is its “link” element. The above example uses it to link to a map image that displays the location of the Severe Thunderstorm Warning area. There could also be links to any other supporting resources.

The “category” element can also handle multiple single level categorisation schemes per entry. In this example: warning status, warning type and the affected weather forecast districts.

Try Atom and GeoRSS. You’ll like it!

[tags]atom, georss[/tags]