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GML, NEN3610 and TOP10NL

GML, NEN3610 and TOP10NL. 4 th GML Relay (Emmen). Wilko Quak. Overview. NEN3610 and its history TOP10NL – a model on top of NEN3610 Transforming the model to GML Questions. History of NEN3610. Originated by Ravi (Network Organization for Geo-Information) First base model in 1992

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GML, NEN3610 and TOP10NL

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  1. GML, NEN3610 and TOP10NL 4th GML Relay (Emmen) Wilko Quak

  2. Overview • NEN3610 and its history • TOP10NL – a model on top of NEN3610 • Transforming the model to GML • Questions GML, NEN3610 and TOP10NL

  3. History of NEN3610 • Originated by Ravi (Network Organization for Geo-Information) • First base model in 1992 • Exchange format NEN1878 GML, NEN3610 and TOP10NL

  4. New NEN3610 (work started in 2003) Prerequisites: • Based on International Standards (ISO, OGC) • Backwards compatible with old NEN3610 • Should be a base for the exchange of all geo-data in the Netherlands (Top-Down approach) • Extensible GML, NEN3610 and TOP10NL

  5. NEN3610 specifications • Nationwide unique identifiers • Temporal model useful for change only updates • Fully described in UML • GML Application Schema is automatically derived from the UML model. • The model is not complete by itself; it is a starting point for sectors that should make a Sector Model • One base class ‘GeoObject’ and about a dozen subclasses. GML, NEN3610 and TOP10NL

  6. NEN3610 – base class: GeoObject • Unique nationwide Identifier • Temporal attributes can be used for incremental updates • Almost all attributes are optional GML, NEN3610 and TOP10NL

  7. NEN3610 – subclasses • Road • Water • Railroad • Terrain – area with specific landuse • Building • Construction – bridges, telephone poles etc. • Dyke – very important in the Netherlands • Cables – underground • RegistrationalArea – province, municipality boundary • GeographicArea – areas with vague boundaries (like the ‘Lake District’ or ‘the Alps’) GML, NEN3610 and TOP10NL

  8. NEN3610 the UML Model GML, NEN3610 and TOP10NL

  9. NEN3610 – temporal model • Four temporal attributes for version management and incremental updates. • objectBeginTime and objectEndTime indicate the lifetime of an object. • If an attribute changes a new version is shipped with a new versionBeginTime. • An object is deleted by shipping it with a non null objectEndTime. • Two temporal attributes for when the object changed in the real world: beginTime and endTime GML, NEN3610 and TOP10NL

  10. Advantages of a nationwide base model + Shared definitions + One shared temporal model for all data in the Netherlands - To keep everybody happy almost all attributes are optional and definitions very vague + A published base model is a good starting point for sector models (even if they do not agree with the model) GML, NEN3610 and TOP10NL

  11. Overview • NEN3610 and its history • TOP10NL – a sector model in NEN3610 • Transforming the model to GML • Conclusions GML, NEN3610 and TOP10NL

  12. IM . . TOP10NL IMKICH RWS IMWA IMRO Base model and sector models International standard OGC ISO 191XX NEN3610 National standard Exchange Sector specific Organisation specific GML, NEN3610 and TOP10NL

  13. Making a sector model Sectors that use NEN3610 should choose the most applicable class in NEN3610 and extend it. If no applicable class is found GeoObject can be extended How to extend: • Extending by subclass • Extending by pattern GML, NEN3610 and TOP10NL

  14. Extension by Subclass Create subclass • add attributes • restrict attributes An extension should not contradict with its base class. Any instance of the subclass must be a valid instance of the superclass. GML, NEN3610 and TOP10NL

  15. Multiple Inheritance • If the original hierarchy has more than one level subclassing might result in a multiple inheritance hierarchy. Keep base hierarchy as flat as possible! GML, NEN3610 and TOP10NL

  16. Extension by Pattern • Copy class and attributes of all superclasses • add new attributes • delete unused attributes (when they were optional) • Results in a new stand-alone UML model GML, NEN3610 and TOP10NL

  17. TOP10NL – The first sector-model • TOP10NL is a national 1 : 10 000 topographic dataset of the Netherlands provided by the Dutch Kadaster • Relatively easy because TOP10NL had a lot of influence on the NEN3610 model • Extension by subclass • Multiple Inheritance avoided by making TOP10Object an attribute of every subclass. GML, NEN3610 and TOP10NL

  18. TOP10NL – the complete model GML, NEN3610 and TOP10NL

  19. Lessons learnt from modeling NEN3610 and TOP10NL • If you want to understand your own data try to make a model that fits. • Keep your model as simple as possible • Make a 1-level hierarchy at most • Give definitions of all classes and attributes (preferably also in English) GML, NEN3610 and TOP10NL

  20. Overview • NEN3610 and its history • TOP10NL – a model in the NEN3610 family • Transforming the models to GML • Questions GML, NEN3610 and TOP10NL

  21. Automatic Translation of UML model UML UML Application Guidelines Schema model (XMI) Encoding Rules ShapeChange ShapeChange (Java, Servlet) (Java program) Configuration Configuration (XML) (XML) GML GML Application Application Schema Schema (XML Schema) (XML Schema) http://www.interactive-instruments.de/ugas/ GML, NEN3610 and TOP10NL

  22. Consequences of Automatic Translation Because the GML Schema depends for 100% on the UML model every choice you make in UML is directly reflected in GML: • You only have to worry about the UML model • Extension by pattern gives different schemas than extension by subclass • Every typo is a bug GML, NEN3610 and TOP10NL

  23. Extension by Subclass: Consequences for XML Schema • The resulting GML lives in two nameSpaces (nen3610 and top10nl) • The sector model includes the definition of the base model and only describes the changes. • Every extension results in a substitutionGroup in the application schema. • Automatic translation of restrictions from UML is tricky. Manual post-processing of the schema is sometimes needed. • Some restrictions cannot be expressed in XML-Schema GML, NEN3610 and TOP10NL

  24. NEN3610 – GML application schema • The NEN3610 UML Model has been automatically converted to a GML application schema (NEN3610.XSD) This software was modified to partly overcome the problems with restrictions in subclasses • TOP10NL can include the NEN3610.XSD from their own schema. GML, NEN3610 and TOP10NL

  25. Extension by pattern: Consequences for XML Schema • Simple document structure • It is not clear from the schema that the sector model is an extension of the base model GML, NEN3610 and TOP10NL

  26. GML design choices in TOP10NL (what’s your opinion?) • Extension by subclass resulting in many substitutionGroups. • lang=“nl” attribute to encode language of geographic names. (this should be part of GML). • Use of objectBeginTime and objectEndTime enables incremental updates • Choice of UTF8 as character encoding: Reli?34f Ge?34lectrificeerd GML, NEN3610 and TOP10NL

  27. Questions? GML, NEN3610 and TOP10NL

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