At FOSS4G 2009 I finally went to a code sprint, partly as a form of meditation, and partly to see if I had any developer chops left. Well the jury is still out on that, but it was relaxing, and what came out of it was the first release of SimpleWFS.

SimpleWFS is a 100% Java servlet that serves any data in PostGIS via the WFS Simple API. Output formats supported are BXFS and KML, among others (GML and Atom coming soon). My hope is that SimpleWFS can be up and running in under a half hour, exponentially increasing the ease of getting more spatial data on the web.

Please try it out and help improve it.

A recent discussion provoked by this SOA Post Mortem article got me thinking about Service-Oriented Architectures and Web Services in the context of our geospatial industry. The general argument in that article is Web services is just the latest buzzword to justify a big round of IT funding if you don’t do the business transformation work to actually redesign your enterprise around the idea of providing information services.

Sounds like it makes sense, but what does that actually mean? To put it in the context of OGC Web services, I’d phrase it as, WMS, WFS, WCS, etc. represent the SOA concept that needs to die. Just because you put a Web Feature Service API on your roads data doesn’t mean you’ve service-enabled anything. You may have taken the first required step towards a service, but the business transformation work isn’t done.

However, let’s say you figure out that what your end users actually need is a service that reports the pavement quality and last maintenance date of all roads in a certain jurisdiction for long-term strategic planning on infrastructure upkeep. Then you build that “service” using your WFS and its ability to handle sophisticated queries. Now you have what I’d call a real service providing real identifiable business value.

So the OGC suite of data delivering Web services is more of a meta-service architecture, or spatial data infrastructure, upon which real value-oriented services can be built. But don’t think you’ve created much value in your organization by simply standing up out-of-the-box OGC services without going the next step and figuring out what applications your data users actually need.

I was at the Earth Science Information Partners (ESIP) meeting last week, and was a little surprised at how much these folks like KML and GeoRSS. OGC stalwarts generally think of simple encodings like these as just good enough to get the job done, if the job you’re doing is pretty simple. The jobs of ESIP members is not, however, simple.

This group is comprised of NASA researchers and other earth, air and water scientists who regularly deal with multi-terabyte databases of satellite imagery and other GIS data sets, so you’d imagine that they would be quite content with their high-end GIS systems. But while there was certainly plenty of industrial strength GIS going on, a good third of the attendees came to the KML and GeoRSS Birds of a Feather session. This made me realize two things:

1. The work we did in OWS-5 on defining how to output KML from a WFS will be very useful
2. We’d better tell people about it so they don’t duplicate our efforts

So at this point you’re probably saying, “get to the point. How do you output KML from WFS?” The easy way is to just get software that does it. In OWS-5, the open source Geoserver and Galdos Systems’ commercial product Cartelinea implemented this functionality. If you have your data in PostGIS, ArcSDE, Oracle Spatial, or Shapefiles, just set up the Geoserver or Cartelinea to server that data via the WFS API and you get KML support for output automagically.

If you want to know how to code your own support, you’ll need to read the upcoming revision to the “Styled Layer Descriptor profile of the Web Map Service Implementation Specification”, but I’ll give you the 30-second version here.

A WFS outputs only data (usually in GML format). KML, however, is data plus styling rules. So to control the output of KML from a WFS, you specify the data you want with a normal WFS request, but you also specify the styling rules using the Styled Layer Descriptor (SLD) language. We call this combination of data request API and style configuration a Feature Portrayal Service (FPS). It’s pretty much a melding of the WFS and WMS APIs. So if you’re familiar with WMS, WFS, and SLD, implementing FPS is straightforward. Just read that SLD profile of WMS document and let me know how it goes.

In the OGC Mass Market Geo Working Group meeting yesterday, I presented the preliminary findings of the group brainstorming about the future of KML in the OWS-5 testbed. Most of what was discussed isn’t ready for prime time, so I’ll wait to talk about for a few months, but one critical point that everyone should understand is that KML is, always has been, and will continue to be about mapping/geospatial visualization. Don’t use KML as a data storage or archival format. That’s what GML is for. Yes, KML has some geographic coordinates in there, but KML’s ability to act like a GIS format–attaching other data properties to the geography, typing them, and putting metadata on it all–is weak.

The right way to think about the geographic information “workflow” is to have a spatial database that serves up data to the Web via the Web Feature Service (WFS) API in some flavor of GML. Soon, OGC will specify how that WFS should serve up KML using the existing WFS API plus some extra information to describe the transformation–probably using SLD. The authoritative data will still reside in the spatial database. The KML will just represent one cartographic view of the data at a particular point in time.

This is simply what geospatial Web services are about IMHO. Let me quote John Kim from the Mass. DOE:

Hi everyone,

We just launched our first set of thematic maps yesterday on our
State’s Special Ed data. Please check it out if you have a chance.

Here is an example using Boston -
http://profiles.doe.mass.edu/home.aspx?orgcode=00350000&view=sped#

As an FYI, we used MassGIS’ GeoServer to make our WMS and WFS
requests.

The DOE is publishing education statistics in table and map form on a web page. Pretty standard so far. But clicking a town on the map zooms to that town and changes the caption of the map to display the graduation rate for that town! I’d guess that the map clicking and zooming is via a WMS interface, and the caption change uses the WFS interface (but that could be leveraging the WMS too via the GetFeatureInfo operation).
I used to consult to MassGIS in the 90s, and it’s nice to see the vision we were advocating about the integration of web services across government agencies bearing fruit. MassGIS has done a ton of great service-oriented work over the years and has won many awards for it. I hope this application gets the recognition it deserves.