An open software framework for Web Service-based geo- processes Theodor Foerster FOSS4G 2006 – Lausanne, Switzerland.

An open software An open software framework for Web framework for Web Service-based geo-Service-based geo-

processesprocessesTheodor FoersterTheodor FoersterFOSS4G 2006 – Lausanne, Switzerland

Theodor Foerster http://www.52north.org 2

Contents

•Motivation•The standard•The architecture•The use case: generalization•Getting involved

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Motivation

•Geospatial data available on the web•Network capacity and computational power available

•Geospatial information is carried out by geo-processes (buffering, generalization,…)

Web-based geo-processes

•Web-based geo-processes should be interoperable

Standard for web-based geo-processes

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Additional benefits

• Interoperable web-based geo-processes- Improve knowledge exchange through the web

Within a communityThrough out domains

- Geo-processes become easily adoptable- Provide high scalability for clients- Web-based geospatial information next step!

Geo-processes become interoperable through Web Services

•OGC web-enables geo-processes through the Web Processing Service (WPS) specification

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Notion of the WPS

•Service communication based on HTTP and XML•No limitations on certain types of processes•No limitations on the data

- Supports raster and vector data- Literal variables (e.g. buffer size)

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WPS operations

•GetCapabilities- Service description- Access description- Brief process descriptions

•DescribeProcess- Full process description

•Execute- Process execution

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<Capabilities version="0.4.0“> <ows:ServiceIdentification>

<ows:Title/> <ows:Abstract/> <ows:Keywords/> …

</ows:ServiceIdentification><ows:ServiceProvider/>

<ows:ServiceContact/> </ows:ServiceProvider> <ows:OperationsMetadata>…<ows:Operation name="Execute“/> </ows:OperationsMetadata> <ProcessOfferings>

<Process><ows:Identifier>Buffer</ows:Identifier></Process>

</ProcessOfferings></Capabilities>

http://geoserver:8080/wps/WebProcessingService?REQUEST=DescribeProcess&Identifier=Buffer&SERVICE=WPS&VERSION=0.4.0

<ExecuteResponse><ows:Identifier>Buffer</ows:Identifier><Status/><DataInputs>…</DataInputs><OutputDefinitions>…</OutputDefinitions><ProcessOutputs><Output><ows:Identifier>BufferResult</ows:Identifier><ComplexValue schema =“schemaNS”>$XML_Geometries</ComplexValue></Output></ProcessOutputs></ExecuteResponse>

<ProcessDescriptions><ProcessDescription <ows:Identifier>Buffer</ows:Identifier> …<DataInputs> <Input> <ows:Identifier>geometry</ows:Identifier> <ComplexData defaultSchema=“schemaNS"/> <MinimumOccurs>1</MinimumOccurs> </Input> <Input> <ows:Identifier>width</ows:Identifier> …<LiteralData> <ows:DataType ows:reference="xs:int"/> …<ProcessOutputs> <Output> <ows:Identifier>BufferResult</ows:Identifier> <ComplexOutput defaultSchema=“schemaNS“/> … </ProcessDescriptions>

http://geoserver:8080/wps/WebProcessingService?REQUEST=GetCapabilities&SERVICE=WPS

<Execute><ows:Identifier>Buffer</ows:Identifier><DataInputs><Input> <ows:Identifier>geometry</ows:Identifier> <ComplexValue schema=“schemaNS”> $XML_Geometries </ComplexValue></Input><Input> <ows:Identifier>width</ows:Identifier> <LiteralValue>100</LiteralValue></Input></DataInputs></Execute>

WPS in action - Buffering

Client WPS

Network

<Execute> request

<Execute> response

<GetCapabilities> request

<GetCapabilities> response

<DescribeProcess> request

<DescribeProcess> response

Inspired by P. Schut’s presentation at the OGC TC Meeting in Huntsville 2006: “WPS RFC responses”

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Additional Features

Supports long-term processes by storing- Handles drawback of HTTP- Avoids recalculation- Status of processes is callable

•Supports chaining (limited)- For data retrieval & processing

•Standardized error messages

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Design goals

•Pluggable•Scalable•Easy to install•Standards compliant

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Framework architecture

Web Processing ServiceWeb Processing Service

WPSGetCapabilities ExecuteDescribeProcess

Algorithms Repository

…

…

Douglas Peucker Algorithm

Data Handler Repository

…

…

GML Data Handler

Communication over the web using HTTP

WPS-clientWPS-client

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Implementation

• Implementation available at 52north under GPL license• Implements all features of the specification

- Storing process results- ComplexReferences

• Fully java-based, running on tomcat• Incorporated APIs:

- Servlet API- Xml-beans- JTS

• Service plus client (JUMP plug-in) available • Basic data handlers• Implementation applied for SWE and generalization

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Use case: generalization

• Geospatial data geospatial information- Scale- User & use

• Model and cartographic generalization• ITC’s generalization research project

- Automated web-based generalization- User-centered generalization- Focus on Dutch topographic data

• First example: simplification- Reduces the number of geometries- Deletes unimportant aspects of data- Important for mobile applications- Mostly not satisfying in cartographic terms

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Example – Simplification

Registering the service and configuring your process…

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Example – Simplification

•…Visualize the result!

original data processed result

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Outlook

• Integration into geoserver/geotools as DataStore

•Adding more data handlers (GML 3.x)• Improving the communication mechanisms

- Asynchronous communication- Incorporating notification mechanisms

•Enabling smart storing- WFS- WCS

•Giving feedback to OGC

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More information

•52n incubator Wiki- Documentation

InstallationExamples

- Binaries and sources- CVS access on sourceforge

•Accessible through the Processing home on the Wiki or directly:

- http://incubator52n.de/twiki/bin/view/Processing/52nWebProcessingService

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Thank youfor your attention!

Watch out for other 52north presentations @Foss4G!

http://www.52north.org

Theodor Foerster

Hengelosestraat 997514 AE EnschedeTel: +31 (0)53 4874373 [email protected]://www.itc.nl