WMS and RDF - For fun and foaf !

At @Semantics we've long been playing with Web Mapping Servers. Recently we've connected them to the world of RDF, RDQL and FoaF. Read a head for an explanation - or simply jump to the demo

So Web Mapping Servers (WMS) are basically web servers which generate an image of some geographic area or 'feature' based on some standard info in the URL. The structure of this URL is defined by the open gis consortsum. Fields in the URL allow for things like selecting specifc regions regions or styles.

Now in the GIS world people think in 'Layers' and 'Features' - which really are just images which are overlayed on top of each other; each containing something specific; e.g. roads, rivers, a landmask. And when stacked together they make up a pretty map.

Layers generally have names; like 'rivers' or 'rabbit-counts'. Give this example a spin to get an idea of the concept - you can switch layers on and off. At this point you may want to take note - do a view-source - of the fact that some of the data actually comes from a different server ran by TSA rather than from us. In fact - your browser fetches their layers (e.g. the rivers) directly from their WMS server without even touching our WMS server. WMS servers of the wolrd unite - Federated Fusion in action!

Recently we created a bit of an unusual deviation (which kind of breaks the WMS/1.1 specification as it makes the 'layer' non deterministic and no longer pre-defines it in the Capabilities file) by allowing an 'RDQL' query as a layer name.

RDQL is a query language for RDF - and the basis of what we call the semantic web.

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So what happens is that we define a layer as an RDQL query - i.e. some query which returns the things to plot on the map (and their positions) - and then dynamically generate the map.

Now one of the very neat thing is that in RDQL you can specify the data soruce as a URI - and it can point to any valid RDF source. Including a file on your site.

Hence you now have a map plotting server which can plot your maps - and best of all; the result is a URI which you simply can include in your web page.

Give it a spin at http://demo.asemantics.com/biz/swad-e/rdqlplot.pl.

And once you are done - set up your own foaf - add your foaf url to the database -or- use the above url to create a nice map of yourself in your own environment.