Development of Semantically Aware Workflow Engines for GEOspatial Web Service Orchestration

Open Grid Forum 20 (OGF20)7th May, 2007

Gobe Hobona(University of Newcastle)

Motivation for Geo-Workflows

• Geospatial processes– Route finding– Constructive Area Geometry– Cartographic generalisation– and several others

• Scheduled tasks– Monitoring geosensors– Backing up geospatial databases

• Integration with OGSA– Provision of geospatial operations– Provision of geospatial databases

An Example Geospatial WorkflowWorkflow Enactor

WFS

WPS 1Generalise

WPS 2Clip

Challenges

• No OGC Workflow Specification

• SOAP/WSDL interface

• Geospatial data inherently very large

• Synchronicity

• Support for OGSA execution and resource management services

SAW-GEO

• A semantically-aware workflow engine for orchestrating geospatial web services

• Involves the Business Process Execution Language (BPEL)

• Related Studies– R. Lemmens, A. Wytzisk, R. d. By, C. Granell, M. Gould, and P. van Oosterom (2006),

"Integrating Semantic and Syntactic Descriptions to Chain Geographic Services ," IEEE Internet Computing, vol. 10, pp. 42-52.

– P. Yue, L. Di, W. Yang, G. Yu and P. Zhao (2007), "Semantics-based Automatic Composition of Geospatial Web Service Chains", Computers & Geosciences , vol. 33, Issue 5, pp. 649-665

System Components

• ActiveBPEL workflow engine

• Globus Toolkit 4– Proxy Service

• Geospatial web service containers (e.g. Geoserver)– Web Feature Service (WFS)– Web Coverage Service (WCS)– Web Processing Service (WPS)– Web Map Service (WMS)*

• BPEL Editors– ActiveBPEL Designer– OMII-BPEL

Alternatives Considered

• Workflow Enactors– Taverna– Netbeans Enterprise Pack– Intalio PXE – now Apache ODE

• SOAP-based web service containers– Apache Axis– JAX-WS (now pre-built into standard Java runtime)

Evaluation

• Need to examine scenarios varying in data availability, data volumes, data security, computational load, interface etc

• EDINA collaboration will allow for testing of security issues

• Performance with multiple use (increasing number of nodes as orchestration becomes more complex)

Conclusions

• BPEL suitable for orchestrating grid-based OGC web services

• Support for SOAP/WSDL important for integration of OGC and OGSA services

• Some issues remain unaddressed within geo services e.g. asynchronous invocation

• SAW-GEO User Evaluation scheduled for Nov 07 – Dec 07

Acknowledgements

• SAW-GEO is funded by the Joint Information Systems Committee (JISC) through the Grid/OGC Collision Programme

• Collaboration with the North East Regional e-Science Centre (NEReSC)

• Thanks to ITC (Netherlands) and LAITS (George Mason University) for access to Web Processing Services