I was sending an email to the FRUGOS list about data processing with GDAL and OGR, and wrote that there is low-hanging fruit in the form of an open source graphical data processing model builder. One attendee of last week's meetup said that the ArcGIS model builder was the only thing he couldn't do without. I met another open source GIS user this summer who also expressed an appreciation for the model builder despite the overall awkwardness of the geoprocessing tool. People love GDAL and OGR. People love graphical modeling. I think we can have these and the benefits of open source as well.
For the Pleiades project we are authoring custom Plone content types using ArchGenXML. We design the content package and its classes using ArgoUML class diagrams. ArchGenXML parses the exported XMI file and creates Plone Archetype based classes -- Python code and scaffolding. ArchGenXML is a remarkable product, allowing someone with no specific Python skill to produce functional Python packages for use in Plone. I believe it would make an excellent starting point for a graphical data processing modeler:
Create a activity diagram in ArgoUML.
Export to XMI.
Parse, adapting the ArchGenXML code, and generate Python modules using gdal.py and ogr.py to execute the diagrammed processes.
The result: a highly portable, visually documented, open source, data processing package.