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GML, NEN3610 and TOP10NL

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Title: GML, NEN3610 and TOP10NL


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

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

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

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.

6
NEN3610 base class GeoObject
  • Unique nationwide Identifier
  • Temporal attributes can be used for incremental
    updates
  • Almost all attributes are optional

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)

8
NEN3610 the UML Model
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

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)

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

12
Base model and sector models
International standard
OGC
ISO 191XX
NEN3610
National standard
Exchange
Sector specific
Organisation specific
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

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.

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!
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

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.

18
TOP10NL the complete model
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)

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

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/
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

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

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.

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

26
GML design choices in TOP10NL (whats your
opinion?)
  • Extension by subclass resulting in many
    substitutionGroups.
  • langnl 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

27
Questions?
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