Model-Driven Web Feature Service A Way Towards Enhanced Semantic Interoperability Peter Staub, ETH...
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Transcript of Model-Driven Web Feature Service A Way Towards Enhanced Semantic Interoperability Peter Staub, ETH...
Model-Driven Web Feature Service
A Way Towards Enhanced Semantic Interoperability
Peter Staub, ETH Zurich
FOSS4G 2007 – Victoria B.C., September 26, 2007
Peter Staub, ETH Zurich 2
Overview
• Data modeling and semantic interoperability: Fundamentals
• Research project mdWFS
• Why a model-driven WFS? Enhancements in semantic interoperability
• Concepts, methods
• Prototype implementation
Peter Staub, ETH Zurich
What is Interoperability?
3
Swiss plug does not fit American socket
So, an appropriate adaptor plug (and a voltage transformer) is needed!
I – Modeling and Interoperability Fundamentals
Interoperability: Format Support + Data Model TransformationInteroperability: Format Support + Data Model Transformation
230V ~50 110V ~60
Peter Staub, ETH Zurich
Data Modeling and Semantic Interoperability
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PIM>PSM Mapping
GML App.Schema Logical/Physical
Schema A (PSM)
<<Model>>
<<derive>> <<derive>>
Logical/PhysicalSchema B (PSM)
<<Model>>
Encoding
GMLInstanceDocument
Database A, Transfer format A
<<instantiate>>
Database B, Transfer format B
<<instantiate>>
MOF
<<Metamodel>>
<<instantiate>> <<instantiate>>
MetamodelCSL X
<<Metamodel>>Metamodel
CSL Y
<<Metamodel>>
Schema Translation
<<derive>>
Conceptual Schema Mapping
<<derive>>
:Instance Translation
<<instantiate>> <<instantiate>>
ConceptualSchema A (PIM)
<<Model>>
ConceptualSchema B (PIM)
<<Model>> Formal mapping
Real World Real World
Application Domain„Model“ B
Application Domain„Model“ A
I – Modeling and Interoperability Fundamentals
Peter Staub, ETH Zurich
Project mdWFS
Web-based cross-border GIS: a regional planning use case
What are the shortcomings of existing approaches?
Overcoming these shortcomings with a model-driven WFS
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„Model-Driven Approach for AccessingDistributed Spatial Information Using Web Services“
II – Project mdWFS
Peter Staub, ETH Zurich
Problem and Requirements
Shortcomings of OGC Web Services [OWS]:• OWS allow for syntactic interoperability but not for semantic
interoperability
Preconditions for a web-based semantic transformation on the conceptual level
• Machineable CSL for data models• Formal language for expressing schema mapping rules• Web service interface
Web service requirements• Access to geospatial data based on conceptual source data
schema and conceptual target data schemas• Interoperability with existing OWS: WFS
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II – Project mdWFS
Peter Staub, ETH Zurich
mdWFS Interface
Idea: model driven Web Feature Service mdWFS
• Extension of OGC WFS specification
• Ability to store and deliver conceptual models (UML/XMI)
• New operation DoTransform() enables WFS carrying out semantic transformations
• Each semantic transformation results in an according set of WFS feature types
• WFS is configured by target schema at conceptual level!
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II – Project mdWFS
Peter Staub, ETH Zurich
WFS Protocol Extensions for mdWFS
Specification of communication protocol for mdWFS new request parameter SERVICE=mdWFS (default: WFS)
Specification of WFS protocol extensions
GetCapabilities
WFS: FeatureTypeList
mdWFS: SchemaList
DescribeFeatureType
WFS: XMLSchema (transfer format schema)mdWFS: XMI (data model)
GetFeature
new request DoTransformperforms semantic transformation and configures a standard WFS
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III – mdWFS: Concept and Methods
Peter Staub, ETH Zurich
What is needed?
• Metamodel: UML 2 profile for geospatial applications (e.g. Interlis CSL)
• Model Parser to convert models (textual notation) into XMI 2.1
• Language specification for semantic model mappings [UMLT]: Extension of UML, Activity diagram
• Model editor to create conceptual model mappings using UMLT
• Transformation operations to execute semantic transformations
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III – mdWFS: Concept and Methods
Peter Staub, ETH Zurich
Schema Mapping Language UMLT
Requirements:• Comprehensible for non-computer scientists• Metamodel, HUTN (Human Useable Textual Notation)• Visual, textual AND XML (i.e. XMI) representation• Application of international standards
Basic principle:• Independent extension of UML metamodel• Metamodel of UMLT as UML 2 model• EBNF (extended Backus-Naur form) for UMLT grammar
specification
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IV – UMLT Specification
Peter Staub, ETH Zurich
Schema Mapping Language UMLT: Superstructure
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IV – UMLT Specification
Peter Staub, ETH Zurich
Schema Mapping Language UMLT: Elements
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IV – UMLT Specification
Peter Staub, ETH Zurich
UMLT Example: Source and Target Data Model
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V – Prototype Implementation
Peter Staub, ETH Zurich
UMLT Example: Transformation Model
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Centroids
V – Prototype Implementation
Peter Staub, ETH Zurich
UMLT Example: Trafo. Model in Model Editor
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V – Prototype Implementation
Peter Staub, ETH Zurich
7ili2ora
Prototype Implementation
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Client = Target System
Model B: UML/XMI
ORACLEORACLE
Server = Source System
Model A: UML/XMI
0
mdWFS
WFSWFS
1Request model catalogue
2Provide model catalogue
3Order required model
4Send ordered model A [XMI]
5 Establish Model Mapping ABili2ora
SQL/Java
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AB
6DoTransform-Request
Model B + Trafo. Model AB [XMI]
deegree
9Model B
DoTransform-Response10
GetCapabilitiesDescribeFeatureType
GetFeature11
V – Prototype Implementation
Peter Staub, ETH Zurich
Conclusion, Lookout
1. Current evolution of GIS: use of CSL (precond. for semantic Trafo)But: metamodels/profiles and „modeling styles“ differ in detail
2. mdWFS: semantic transformation is established at conceptual level; independent from any format or (DB-)system
3. Concept based on GI standards allows for integration into existing (OWS based) infrastructures
To do:• Finish implementation of transformation operations• Further development of UMLT• Prototype evaluation in the context of geodata infrastructures
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Peter Staub, ETH Zurich
Thank you very much!
Acknowledgements
German Federal Agency for Cartography & Geodesy
Swiss Federal Office of TopographyTU Munic project teamColleagues at ETH Zurich
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