Copyright © 2009 Open Geospatial Consortium, Inc.Copyright © 2009 Open Geospatial Consortium, Inc.
3 WSMO Web Service Modelling Ontology
WSMX Web Service Modelling eXecution engine
XML eXtensible Markup Language
3.2 UML notation
Most diagrams that appear in this standard are presented using the Unified Modeling Language UML static structure diagram, as described in Subclause 5.2 of OGC 2007.
4 Introduction
This section starts with an overview over the OGC activities and achievements in the context of Geoprocessing Workflows in the past. This serves as a starting point for
defining the term Geoprocessing Workflow followed by explanations of relevant concepts for challenges targeted at the OWS-6 GPW testbed. The presented concepts are evaluated
with a proof-of-concept implementation at the end of this document.
4.1 Basic concepts for OWS Workflows
The Open Geospatial Consortium has focused on spatial related workflows since several years. Starting with ISO19119 ISO 2001 the OpenGIS Consortium OGC and ISO
TC211 have jointly developed an international standard for geospatial service architecture including the description of different workflow patterns see section 4.2.
Additionally, several testbeds explored Geoprocessing Workflows in detail: In the OWS- 2 testbed, service chaining with the Business Process Execution Language BPEL was
elaborated. Figure 1 shows the basic architecture.
4
Copyright © 2009 Open Geospatial Consortium, Inc.Copyright © 2009 Open Geospatial Consortium, Inc.
Discovery Client
WOS
Map Viewer Client
CPS
Data Services Portrayal Services
Catalog -Registry Services
Processing Services Application Services
Bind
= OpenGIS Service Interface
Find
WFS
WMS
Encodings
GML ESML
Service Metadata
WMS Context
XIMA
WSDL Image
Catalog
Image Metadata
Publish
Service Catalog
Image Exploitation
Workflow Manager
BPEL
WCTS WICS
WCS
SensorML
WorkflowTask Services
WfCS
Invoke
Execute Control
Figure 1. OWS-2 Architecture
Details are described in OGC 2004 but it is important to note that a BPEL workflow engine was used and labeled as a Workflow Chaining Service WfCS. Therefore a WfCS
is a class of Workflow and Task Services as defined in ISO 19119 but is not defined further with a fixed interface and therefore can be only regarded as a concept rather than
a service in an OGC sense. Since the workflow is hidden behind the vendor specific WfCS interface, the opaque service chaining pattern was applied. Additionally, OGC
2004 describes only synchronous workflow interactions but identified a need for asynchronous service interaction as well. All data was passed by reference since all
services processing and data supported this type of data transaction.
The follow-up OWS-3 testbed also relied on BPEL as the workflow language. As shown in figure 2, a workflow consisting of Web Coordinate Transformation Service WCTS
was implemented for a remote sensing scenario.
