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Workflow Enactment of Grid-Enabled Geospatial Web Services

Workflow Enactment of Grid-Enabled Geospatial Web Services. Gobe Hobona , David Fairbairn, Philip James. UK e-Science All Hands Meeting - 12 th September 2007 - Nottingham. Overview. Background OGC Web Services Workflow Enactment SAW-GEO Architecture User interface – Geoportal

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Workflow Enactment of Grid-Enabled Geospatial Web Services

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  1. Workflow Enactment of Grid-Enabled Geospatial Web Services Gobe Hobona, David Fairbairn, Philip James UK e-Science All Hands Meeting - 12th September 2007 - Nottingham

  2. Overview • Background • OGC Web Services • Workflow Enactment • SAW-GEO Architecture • User interface – Geoportal • Conclusions

  3. Background • Open Geospatial Consortium (OGC) • ISO19119 and OGSA • JISC Grid/OGC Collision Programme • Security : SEE-GEO • Workflow : SAW-GEO • OGC Interoperability Experiments (OWS-4)

  4. OGC Web Services • Web Feature Services (WFS) • Disseminates vector geospatial data • Web Map Services (WMS) • Generates geovisualisations/maps from any geo-data source • Web Coverage Services (WCS) • Disseminates raster geospatial data • Web Processing Services (WPS) • Runs geocomputational models or geospatial operations on user-supplied datasets

  5. Sample OWS Request Messages <GetCoverage service="WCS" version="1.0.0" xmlns="http://www.opengis.net/wcs" xmlns:nurc="http://www.nurc.nato.int" xmlns:ogc="http://www.opengis.net/ogc" xmlns:gml="http://www.opengis.net/gml" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.opengis.net/wcs http://schemas.opengis.net/wcs/1.0.0/getCoverage.xsd"> <sourceCoverage>nurc:Arc_Sample</sourceCoverage> <domainSubset> <spatialSubset> <gml:Envelope srsName="EPSG:4326"> <gml:pos>9.420000076293944 42.20000076293945</gml:pos> <gml:pos>11.819999694824217 43.90000049273173</gml:pos> </gml:Envelope> ….. </domainSubset> <rangeSubset><axisSubset name="Band"><singleValue>1</singleValue></axisSubset></rangeSubset> <output> <crs>EPSG:4326</crs><responseCrs>EPSG:32626</responseCrs><format>TIFF</format> </output> </GetCoverage> <wfs:GetFeature service="WFS" version="1.0.0" outputFormat="GML2" xmlns:topp="http://www.openplans.org/topp" xmlns:wfs="http://www.opengis.net/wfs" xmlns:ogc="http://www.opengis.net/ogc" xmlns:gml="http://www.opengis.net/gml" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.opengis.net/wfs http://schemas.opengis.net/wfs/1.0.0/WFS-basic.xsd"> <wfs:Query typeName="topp:states"> <wfs:PropertyName>topp:STATE_NAME</wfs:PropertyName> <wfs:PropertyName>topp:PERSONS</wfs:PropertyName> <ogc:Filter> <ogc:BBOX> <ogc:PropertyName>the_geom</ogc:PropertyName> <gml:Box srsName="http://www.opengis.net/gml/srs/epsg.xml#4326"> <gml:coordinates>-75.102613,40.212597 -72.361859,41.512517</gml:coordinates> </gml:Box> </ogc:BBOX> </ogc:Filter> </wfs:Query> </wfs:GetFeature>

  6. Sample OWS Response Messages … </gml:featureMember> <gml:featureMember> <topp:states fid="states.40"> <topp:the_geom> <gml:MultiPolygon srsName="http://www.opengis.net/gml/srs/epsg.xml#4326"> <gml:polygonMember> <gml:Polygon> <gml:outerBoundaryIs> <gml:LinearRing> <gml:coordinates decimal="." cs="," ts=" "> -77.476082,39.719528 -78.096222,39.725368 ……74.984978,41.099285 -74.989265,41.081665 -74.966675,41.082581 -77.476082,39.719528 </gml:coordinates> </gml:LinearRing> </gml:outerBoundaryIs> </gml:Polygon> </gml:polygonMember> </gml:MultiPolygon> </topp:the_geom> <topp:STATE_NAME>Pennsylvania</topp:STATE_NAME> <topp:PERSONS>1.1881643E7</topp:PERSONS> </topp:states> </gml:featureMember> <gml:featureMember> …. • NCOLS 522 • NROWS 300 • XLLCENTER -1.6878262291489 • YLLCENTER 54.93369175561999 • CELLSIZE 3.013533976228086E-4 • NODATA_VALUE -9999.0 • 62.20000 61.70000 61.20000 61.20006 60.7000 60.40000 60.40000 60.09999 59.5 • 61.79999 61.5 61.09999 61.09999 60.7000 60.40000 60.40000 60.20000 60.09999847 • 61.79999 61.5 61.099998 61.09999 60.7999 60.5 60.5 60.5 60.5 • 61.90000 61.59999 61.20000 61.20000 60.9000 60.70000 60.70000 60.79999 60.5 • 62.5 62.20000 61.799999 61.79999 61.79999 61.40000 61.40000 61.09999 60.90000153 • 62.70000 62.40000 62.40000 62.40000 62 61.70000 61.70000 61.40000 61.09999847 • 63.09999 63 62.59999 62.59999 62.4000 62 62 61.79999 61.5 • 63.70000 63.5 63.20000 63.20000 62.9000 62.59999 62.59999 62.40000 62.09999847 • 63.90000 63.70000 63.40000 63.400001 63.0999 62.90000 62.90000 62.59999 62.40000153 • 64.19999 64 63.70000 63.70000 63.5 63.29999 63.299999 63.09999 62.79999924 • 64.40000 64.19999 64 64 63.7000 63.59999 63.599997 63.29999 63.09999847 • 64.90000 64.69999 64.5 64.5 64.4000 64.19999 64.19999 64 63.79999924 • 64 64.90000 64.80000 64.80000 64.5999 64.5 64.5 64.40000 64.19999695 • 64 64 64 64 64 64.80000 64.80000 64.69999 64.5 • 64 64 64 64 64 64 64 64 64 • 64 64 64 64 64 64 64 64 64 • 64 64 64 64 64 64 64 64 64 • 64 64 64 64 64 64 64 65 65.30000305 • 64 64 64 64 64 65.19999 65.5

  7. Grid-enabling OWS • SOAP-based proxy service • Created from OGC XML schemas (XSD) • Requests create temporary datasets • Resource management at two levels • Temporary datasets managed by proxy service • Persistent data managed through OWS e.g. WFS-T • Security limitations • OWS currently do not offer message encryption • Approach to wrap OWS in firewall and allow external access only through proxy service

  8. Geospatial Data is Very Large • Vector data • Thousands of coordinates • Multiple dimensions • Raster data • Thousands of pixels (very high resolution) • Multispectral imagery (200+ band imagery) • Solution • Pass data by URL references and get client to stream data in

  9. Load Experiment

  10. Workflow Enactment • Recognised by both ISO19119 and OGSA • Several options for workflow enactment • SCUFL, BPEL, Keppler etc • Selected BPEL because • OASIS Standard, i.e. WS-BPEL 2.0 • Multi-vendor support including IBM, Sun Microsystems, ActiveEndpoints, Oracle etc • Availability of open source enactors

  11. WS-BPEL Overview • Based on Activities • Basic or Structured • Variables • Declaration • Assignment • Conditionals • Loops • Fault handlers

  12. An Example Geospatial Workflow WPS 1 Generalise WFS Workflow Enactor client WPS 2 Clip Based on OGC OWS-4 GeoProcessing Workflow Scenario

  13. Possible Applications for Geo-Workflows • Emergency Management • Where each activity depends on the result of a previous activity • Geographic modelling • Where several steps are needed before a final model is produced e.g. ESRI Model Builder • Climate Change scenarios • Where a number of possible routes for workflows are possible depending on the state of certain variables

  14. Components • Geoserver • 52North WPS • ActiveBPEL Open Source Engine • Globus Toolkit (GT4) …or Apache Axis 2

  15. SAW-GEO Architecture

  16. Geoportal • User • Browser-based BPEL Upload • Hot deployment • AJAX-based SOAP client • Workflow Monitoring • ActiveBPEL Admin Console • Offers views of deployed processes • Exports a list of available services to the SOAP client as XML • Red font: Developed for SAW-GEO

  17. ActiveBPEL Workflow Engine

  18. Discussion • Importing OGC XSD into SOAP services offered high interoperability • However, variations in how tiers interpreted the XSD • varying namespaces • cyclic imports • Necessary to throw faults at SOAP tier from faults at OGC tiers, because BPEL can handle SOAP faults • Variations in GML between workflow nodes, potentially requiring ‘shim services’ when chaining OWS

  19. Conclusions • SOAP wrappers needed for Grid-enabling OGC web services • OGC XSD appropriate for creating SOAP wrappers • Geospatial data best passed through URL references to avoid overwhelming the workflow enactor • BPEL can support Grid-enabled OGC web services

  20. Future Work • Experimental deployment on the Belfast e-Science Centre (BeSC) DEBUT system • Investigate deployment on upcoming NGS GT4 infrastructure • User Evaluation (November-December 2007) • Volunteers needed – Please register on the website • http://www.edina.ac.uk/projects/seesaw • Integration with SEE-GEO

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