Information Technology Reference
In-Depth Information
Management
There are many standards addressing the management and non-
functional aspects of Web services. Here, we only list some from
W3C's Web Service Activity Statement [35]. For a more comprehensive
list, please refer to [3,35-37].
WS-Policy describes the policies (security, quality of service,
etc.) of entities in a Web services-based system.
WS-Addressing specifies how to describe an endpoint reference
of a Web service, and policies to transmit and route messages
among endpoints.
WS-Transfer defines a SOAP-based protocol to create, update,
and delete Web service-based resources.
WS-Enumeration defines a SOAP-based protocol to enumerate a
sequence of XML elements in large data sets, such as logs, event
streams, and message queues.
1.2.2 Workflow-Related Standards
In Section 1.2.1, we have discussedWeb service-related standards. Some
of them, such as BPMN and BPEL, are related toworkflow. As the theme
of the topic isWeb service-based workflow, next we introduce workflow-
related standards. Among them, the most important one is WfMC's
WorkflowReferenceModel [6], which has laid the foundation in defining
the structure of a workflow system. The reference model first defines a
general glossary to be used in workflow systems, and we have used this
glossary when we introduce workflow technology. The reference model
also includes a reference architecture of a workflow system. In this
architecture, the core component of a workflow system is one or more
workflow engines, and each engine has five interfaces interacting with
other major components in the system. Figure 1.9 illustrates the WfMC
Workflow Reference Model. Now we introduce what a workflow engine
is and how it interacts with other components via five interfaces.
A workflow engine is the software to create, execute, and manage
workflow instances, and facilitate their interactions with human
and automated applications. A workflow system mainly consists of
one or more workflow engines that form workflow enactment services.
