GML, NEN3610 and TOP10NL
4th GML Relay (Emmen)
Wilko Quak
2006-01-26
1
OTB Research Institute for Housing, Urban and Mobility Studies
Naam van de presentatie
Overview
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•
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NEN3610 and its history
TOP10NL – a model on top of NEN3610
Transforming the model to GML
Questions
2006-01-26
GML, NEN3610 and TOP10NL
OTB Research Institute for Housing, Urban and Mobility Studies
2
History of NEN3610
• Originated by Ravi (Network Organization for GeoInformation)
• First base model in 1992
• Exchange format NEN1878
01278.
N200001200001 100000101top10
020110100000
0
0
1
03M26113
G030000
D20000101
04I1
X161310549Y475005000
03M25013
G030000
D20000101
04I1
X183335225Y475005000
03M25263
G030000
D20000101
04I1
X160005000Y494859812
03M24044
G110000
D19930101
04I1 GML, NEN3610
X178992927Y484947328I2
X
2006-01-26
and TOP10NL
3
03M24044
G110000
D19930101
04I1
X178882670Y484888126I2
X
G110000
D19930101
OTB Research Institute for Housing, Urban and03M24044
Mobility Studies
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
2006-01-26
GML, NEN3610 and TOP10NL
OTB Research Institute for Housing, Urban and Mobility Studies
4
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.
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2006-01-26
GML, NEN3610 and TOP10NL
OTB Research Institute for Housing, Urban and Mobility Studies
5
NEN3610 – base class: GeoObject
• Unique nationwide Identifier
• Temporal attributes can be used
for incremental updates
• Almost all attributes are optional
2006-01-26
GML, NEN3610 and TOP10NL
OTB Research Institute for Housing, Urban and Mobility Studies
6
NEN3610 – subclasses
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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’)
2006-01-26
GML, NEN3610 and TOP10NL
OTB Research Institute for Housing, Urban and Mobility Studies
7
NEN3610 the UML Model
2006-01-26
GML, NEN3610 and TOP10NL
OTB Research Institute for Housing, Urban and Mobility Studies
8
NEN3610 – temporal model
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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
2006-01-26
GML, NEN3610 and TOP10NL
OTB Research Institute for Housing, Urban and Mobility Studies
9
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)
2006-01-26
GML, NEN3610 and TOP10NL
OTB Research Institute for Housing, Urban and Mobility Studies
10
Overview
•
•
•
•
NEN3610 and its history
TOP10NL – a sector model in NEN3610
Transforming the model to GML
Conclusions
2006-01-26
GML, NEN3610 and TOP10NL
OTB Research Institute for Housing, Urban and Mobility Studies
11
Base model and sector models
International standard
OGC
ISO 191XX
NEN3610
National standard
Exchange
Sector specific
Organisation specific
2006-01-26
GML, NEN3610 and TOP10NL
OTB Research Institute for Housing, Urban and Mobility Studies
12
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
2006-01-26
GML, NEN3610 and TOP10NL
OTB Research Institute for Housing, Urban and Mobility Studies
13
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.
2006-01-26
GML, NEN3610 and TOP10NL
OTB Research Institute for Housing, Urban and Mobility Studies
14
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!
2006-01-26
GML, NEN3610 and TOP10NL
OTB Research Institute for Housing, Urban and Mobility Studies
15
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
2006-01-26
GML, NEN3610 and TOP10NL
OTB Research Institute for Housing, Urban and Mobility Studies
16
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.
2006-01-26
GML, NEN3610 and TOP10NL
OTB Research Institute for Housing, Urban and Mobility Studies
17
TOP10NL – the complete model
2006-01-26
GML, NEN3610 and TOP10NL
OTB Research Institute for Housing, Urban and Mobility Studies
18
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)
2006-01-26
GML, NEN3610 and TOP10NL
OTB Research Institute for Housing, Urban and Mobility Studies
19
Overview
•
•
•
•
NEN3610 and its history
TOP10NL – a model in the NEN3610 family
Transforming the models to GML
Questions
2006-01-26
GML, NEN3610 and TOP10NL
OTB Research Institute for Housing, Urban and Mobility Studies
20
Automatic Translation of UML model
UML
Application
Schema
model
(XMI)
UML
Guidelines
Encoding Rules
ShapeChange
(Java,program)
(Java
Servlet)
GML
Application
Schema
(XML Schema)
2006-01-26
Configuration
(XML)
http://www.interactive-instruments.de/ugas/
GML, NEN3610 and TOP10NL
OTB Research Institute for Housing, Urban and Mobility Studies
21
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
2006-01-26
GML, NEN3610 and TOP10NL
OTB Research Institute for Housing, Urban and Mobility Studies
22
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
2006-01-26
GML, NEN3610 and TOP10NL
OTB Research Institute for Housing, Urban and Mobility Studies
23
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.
2006-01-26
GML, NEN3610 and TOP10NL
OTB Research Institute for Housing, Urban and Mobility Studies
24
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
2006-01-26
GML, NEN3610 and TOP10NL
OTB Research Institute for Housing, Urban and Mobility Studies
25
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
2006-01-26
GML, NEN3610 and TOP10NL
OTB Research Institute for Housing, Urban and Mobility Studies
26
Questions?
2006-01-26
GML, NEN3610 and TOP10NL
OTB Research Institute for Housing, Urban and Mobility Studies
27