The Potential of WFS

    Web feature Service, WFS, is the logical extension of theprior Web Map Service, WMS, specification from the Open Geospatial Consortium, OGC. (See GeoServer for an open source OWS server) Apart from the questionable proliferation of acronyms, there is a real reason for this. WMS deals with distribution of raster while WFS pushes out vectors. WMS rasters of course may be and often are the result of underlying stores of vectors, but the client sees only the pixel result. On the other hand WFS pushes out the more fundamental mathematics of geometry in the form of another acronym, GML or Geographic Markup Language. The utility of geometry on the client side may be in question, especially in the html world where vectors reside as second class or less citizens. However, a further acronym, SVG, Scalable Vector Graphics, adds vector rendering to the humble browser, opening a new window for graphic clients.

    WFS combined with a vector rendering specification like the W3C’s SVG or Microsoft’s take on the same problem, XAML, extends the simple raster map into a new thing. In vectors all geometries are accessible, all features are potentially event driven, dynamic, interactive, alive. Geometry is a short hand for complex pixel relationships. Instead of empty singular pixels, geometry defines pixel relations in the real number plane. Linear algebra provides very efficient spatial manipulation for scaling, skewing, rotating, and translating Cartesian end points, while geometry fills in the relation(s) between ends. Rendering geometry on the client pulls intelligence back from the server into the local system.

    Unfortunately WFS on the server is still rare, and vector rendering on the browser is only in versions 1.0. Incentive for WFS publication is somewhat lacking until the client rendering is ubiquitous. It is still conceivable that there is value in pushing out vectors as GML for input to other systems, a mere transport mechanism, but the real end goal is direct rendering with event listeners at the client. The obvious early players in the WFS services are government players like the USGS, Census Bureau, County appraisers, FEMA, … which at present have not publicly exposed vectors in a WFS. There are a number of WMS services available, but WFS is still in its infancy. Commercial interest would grow out of the availability of base infrastructure in the government realm.

    There are some early hints. NOAA has recently opened an experimental electronic navigation chart, ENC, web service as WFS to supplement their previous WMS. There is some talk of a WFS published by the Census Bureau sometime in this coming Feb. The delay is curious given the potential benefit for both the government and the public. The Census is actually a member of the OGC, and Paul Daisy, had done some very interesting work back in 2003. The Census continues work on an experimental service but apparently it will not become available until Feb of 2006 at the earliest.

    WFS is vector, optionally bidirectional, and chainable. Each of these attributes is an important step for GIS web services. Vectors are important to client side interaction, bidirectional WFS-T is important for community based data stores, and the ability to chain together published web services unleashes the commercial potential. The three together are potentially revolutionary for GIS web services.

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