OpenGIS Web Feature Services for editing cadastral data Analysis and practical experiences Master of Science thesis T.J. Brentjens Section GIS Technology Geodetic Engineering Faculty of Civil Engineering and Geosciences Delft University of Technology OpenGIS Web Feature Services for editing cadastral data Analysis and practical experiences Master of Science thesis Thijs Brentjens Professor: prof. dr. ir. P.J.M. van Oosterom (Delft University of Technology) Supervisors: drs. M.E. de Vries (Delft University of Technology) drs. C.W. Quak (Delft University of Technology) drs. C. Vijlbrief (Kadaster) Delft, April 2004 Section GIS Technology Geodetic Engineering Faculty of Civil Engineering and Geosciences Delft University of Technology The Netherlands Het Kadaster Apeldoorn The Netherlands i ii Preface Preface This thesis is the result of the efforts I have put in my graduation research project between March 2003 and April 2004. I have performed this research part-time at the section GIS Technology of TU Delft in cooperation with the Kadaster (the Dutch Cadastre), in order to get the Master of Science degree in Geodetic Engineering. Typing the last words for this thesis, I have been realizing more than ever that this thesis marks the end of my time as a student at the TU Delft. However, I also realize that I have been working to this point with joy. Many people are “responsible” for this, but I’d like to mention the people who have contributed most. First of all, there are of course people who were directly involved in the research project. Peter van Oosterom had many critical notes and - maybe even more important - the ideas born out of his enthusiasm improved the entire research. Many thanks go to Tom Vijlbrief, representing the Kadaster, for his helpful comments (on all topics) and for showing the way when it concerned Kadaster issues. Wilko Quak always was available to give technical support. But I’d like to thank especially Marian de Vries. As my direct supervisor, she helped solving technical problems, reviewing new pieces I wrote for this thesis and developing parts of the software. Especially their expertise and pleasant way of working, created the right atmosphere to perform the research in. Besides the scientific interest of people, two people have contributed to the project without any direct interest (I think at least). Here, I have to mention Marco Baars, a good friend and fellow MSc student. He also reviewed my thesis, but more importantly he always has been available for a cup of coffee, lunch or a short walk outside. I’m grateful to my mother, Dorrit Brentjens, who also helped with reviewing my thesis and gave the necessary mental support to me, even during very difficult times for her. For the upcoming years, I hope to work in the same friendly yet professional atmosphere as I’ve experienced during this MSc thesis project. Delft, 28 April 2004 Thijs Brentjens iii Preface iv Contents Contents Preface ............................................................................................. iii Summary .......................................................................................... ix Samenvatting ................................................................................. xiii 1 Introduction ............................................................................. 1 2 Geographic data in distributed environments ........................... 3 2.1 Sharing geographic data sets ................................................... 3 2.1.1 Geographic features .......................................................... 3 2.1.2 Sharing geographic data .................................................... 4 2.1.3 Some cases ..................................................................... 5 2.2 Distributed systems.................................................................. 7 2.2.1 Basics of distributed (geo) database systems........................ 7 2.2.2 The client-server architecture ............................................. 8 2.2.3 Advantages and disadvantages of distributed systems and client-server computing ..................................................... 9 2.3 Interoperable geoprocessing.................................................. 11 2.3.1 Interoperability and interoperable geoprocessing..................11 2.3.2 Problems with interoperability ...........................................12 2.3.3 Open systems and GIS Web Services..................................13 2.4 Final remarks ......................................................................... 15 3 Geometric transactions........................................................... 17 3.1 Database transactions ............................................................ 17 3.1.1 Concurrency control and transactions .................................17 3.1.2 Processing transactions ....................................................18 3.2 Why geometric transactions are complicated ......................... 18 3.2.1 Geometry in transactions ..................................................19 3.2.2 Topologically structured data.............................................20 3.2.3 Spatial constraints ...........................................................21 3.3 Conclusion .............................................................................. 22 4 OpenGIS Web Feature Services .............................................. 23 4.1 OpenGIS Service Framework .................................................. 23 4.2 Relevant technologies for GIS web services ........................... 25 4.2.1 HTTP..............................................................................25 4.2.2 XML ...............................................................................26 4.2.3 Geography Markup Language ............................................28 4.2.4 Filter encoding ................................................................30 v Contents 4.2.5 OpenGIS Web Services: the WMS, WCS and WFS interfaces ..31 4.3 WFS in more detail ................................................................. 36 4.3.1 Basics on WFS.................................................................36 4.3.2 Read-only service: Basic WFS............................................38 4.3.3 Modifying features: Transactional WFS................................40 4.4 Conclusion .............................................................................. 42 5 Case study: Notary sketches new parcel................................. 43 5.1 Case study: the starting point................................................. 43 5.1.1 The role of a notary in cadastral transactions.......................43 5.1.2 Scenario for splitting parcels using a Web Feature Service .....44 5.1.3 Data model.....................................................................45 5.2 The service to draft parcels .................................................... 46 5.2.1 Service architecture .........................................................46 5.2.2 Application logic ..............................................................47 5.2.3 Requirements for the server..............................................49 5.2.4 Requirements for the client ...............................................49 5.3 Web Feature Servers .............................................................. 50 5.3.1 XSQL .............................................................................50 5.3.2 GeoServer: an open source web feature server ....................51 5.4 WFS clients............................................................................. 53 5.4.1 Existing transactional clients .............................................53 5.4.2 Developed client in the case study .....................................53 5.5 Conclusion .............................................................................. 56 6 Suitability of WFS for transactions: analysis........................... 59 6.1 Interoperability testing .......................................................... 59 6.1.1 Server............................................................................59 6.1.2 Clients ...........................................................................60 6.2 Handling transactions............................................................. 63 6.3 Validation of features ............................................................. 64 6.3.1 Validation of single features ..............................................64 6.3.2 Validation of features in their environments.........................66 6.4 Application logic ..................................................................... 67 6.5 Conclusion .............................................................................. 69 7 Conclusions and recommendations......................................... 71 7.1 Conclusions ............................................................................ 71 7.2 Recommendations .................................................................. 72 References ...................................................................................... 75 Appendix A: Glossary....................................................................... 79 Appendix B: Table definitions case study ........................................ 83 vi Contents Appendix C: Client in detail.............................................................. 85 Appendix D: Example Transactional WFS......................................... 91 Appendix E: Open source development GeoServer .........................