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Open Source GML

Open Source GML. Tools and Usage. Overview. Quick Background Organizational biases, GML products Existing Open Source Tools Libraries Generation Consumption Unresolved Issues Conclusions What should you use?. TOPP. Previously Vision for New York Mission:

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Open Source GML

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  1. Open Source GML Tools and Usage

  2. Overview • Quick Background • Organizational biases, GML products • Existing Open Source Tools • Libraries • Generation • Consumption • Unresolved Issues • Conclusions • What should you use?

  3. TOPP • Previously Vision for New York • Mission: • Develop open source digital earth tools • Demonstrate technology projects • Advocate for open, free geographic information • Software Products • GeoServer (Geographic Server) • Virtual Terrain Project (Visual Simulation Client) • GML is core to our products • Java bias

  4. Product: GeoServer • J2EE • Full non-transactional WFS • Reads from PostGIS • Full transactional support

  5. Product: Virtual Terrain • C++/OpenGL • Latest build has WFS import support for generic objects • Cultural objects transitioning to GML encodings • Working on full run-time WFS compatability

  6. Open Source GML Libraries • Java • GML4J (Galdos) • GeoTools (Leeds/TOPP) • OpenMap (BBN) • Geobject? (Polexis) • C++ • OGR (Warnerdam) • Other Languages • ?

  7. Case Study: GML4j • Approach • DOM Parser (tree structure) • Tools to walk tree structure • Advantages • Most general parser • Disadvantages • Memory intensive and slow (DOM) • Thin feature framework

  8. Case Study: GeoTools2 • Approach • SAX parser (event-based) • Directly transformed to internal feature model • Advantages • Fast and low-memory • Rich toolkit available • Disadvantages • Loose generality and flexibility with features • Toolkit somewhat immature

  9. Open Source Generators • GeoServer • Known to have interoperated • Academic • UMN MapServ (planned) • Other academic projects • Nothing packaged • Commercial • Under a dozen

  10. Open Source GML Viewers • Virtual Terrain Project (TOPP) • Beta support via OGR • All internal storage to GML • SVG Viewer • Javascript-based • Nedjo Rogers talk tommorrow • MapServer (UMN), GeoServer (TOPP) • WMS viewing support coming • Non-Productized Viewers • GeoTools, OpenMap

  11. Open Issues • Base Issue • Dealing with the complexity of GML features • Overview • Feature Type Complexity • Internal Feature Types • Schema Proliferation • Projections

  12. Issue: Feature Type Complexity • Issue • Structure and syntax complex • Post-GML, interoperability remains elusive • Proposals • ESRI’s Simple GML proposal • Warnerdam • Conclusions • Adhere to flat feature schemas

  13. Issue: Internal Feature Types • Issue • Tightness of coupling • Tradeoff: power vs. flexibility • Approaches • Generic Models: GeoTools2 • Simple Models: OGR • Conclusions • Simple features will dominate toolkits

  14. Issue: Schema Proliferation • Issue • Representation for common objects • Proposals • Information Communities (OGC) • SEDRIS (MITRE) • Conclusions • Still far away from results • Focus on common schema definitions • Toolkits unsure: GML, RDF

  15. Issue: Projections • Issue • EPSG is standard • Limitations to EPSG database • Approaches • External WKT • Conclusions • Integrated XML encoding required • Coming in GML3

  16. Future Work: GeoTools2 • GML Parsing • Handle non-flat features • GML3 • GML Generation • Integration happening now

  17. Future Work: GeoServer • GeoTools2 Integration (1 month) • Transactional WFS • Internal Filtering • Data Support • Shape, MIF, MySQL, CSV • SLD/WMS (2 months) • Other (ongoing) • GML3 • WCS • Data Formats • ArcSDE, Oracle 9i Spatial

  18. Future Work: Virtual Terrain • Internal representation • Custom text to GML • Generic cultural object representations • Run-time WFS/WCS 3D support • Current imports in 2D functional • Fully interactive 3D scene browsing • Whole Earth Paging • Browser plug-in

  19. Conclusions • Historical reluctance to develop tools • Underlying tech developing (XML, Schema) • Confusion over standard • GML Schema requirement • Some successes • Hesitation with coming of GML3 • Some tools now available • Parsers generally bound to toolkit

  20. Conclusions • More tools will develop • Underlying technologies stabilizing • GML3 (hopefully) will solve • Waiting for the next big thing • Confusion over standards • When to use Open Source • Time to develop not critical • Cost is critical • Vendor independence critical

  21. Conclusions • What to use? • GML4j, GeoTools2, OGR/GDAL • Commercial vendors • URLs • TOPP: http://www.openplans.org • GeoServer: http://geoserver.sourceforge.net • Virtual Terrain: http://vterrain.org • GeoTools: http://www.geotools.org • OGR/GDAL: http://remotesensing.org • PostGIS: http://postgis.refractions.net

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