Validating Web Feature Server for OpenGIS Architectures

The Canadian Geospatial Data Infrastructure is a distributed system maintained by many levels of government, private companies, and non-governmental organizations. The CGDI systems provide services for viewing, retrieving and analyzing spatial information -- information that is generally represented on maps.

The CGDI system is built using open standards from the OpenGIS Consortium that allow the various CGDI systems to share data and maps transparently. One of the newest standards from OpenGIS is the Web Feature Server (WFS) standard, that describes how a server computer and client computer can communicate to edit geographic information over the internet.

Historically, geographic data editing has only been possible with special software running on a single computer. The new WFS standard will allow much wider government and public involvement in the maintainance of spatial databases. For example, a non-governmental organization could provide a WFS with information about grizzly bear sightings, and allow users to add new sightings to the system directly. Or a federal agency could provide a WFS with national road network data, and allow provinces and municipalities to update information directly.

Once spatial databases are more open, more people will be providing information to them, and the probability of more errors rises. It is not enough for an open database to receive new data, in order for the data to be useful it must be "valid". That is, it must follow a baseline set of rules that make sense for the data. For example, new roads should not cross lakes unless they are bridges. New grizzly bears sightings should not occur in Toronto. These are examples of "validation rules".

Many of the validation rules that organizations want to apply to their data are readily subject to automation. Historically, organizations with the financial means have written validation programs from scratch, using whatever tools were generally available. Often this meant the tools were built into proprietary desktop GIS software, and had to be run by hand for new validations.

Our project, funded by GeoInnovations, was to create a spatial data validation framework that organizations could easily reuse for their different data sets, and that could be integrated into a Web Feature Server, so that new data updates could be automatically validated before being added to spatial databases.

Our project delivered the Validation framework, and also integrated it into the GeoServer Web Feature Server. The Validation framework and the GeoServer WFS are both released as "open source" software, which means that other software developers can look at the internals, make changes if they wish, and redistribute the software as they wish.