Web Services Architecture

An overview of

David Booth, Hugo Haas, Francis McCabe, Eric Newcomer, Michael Champion, Chris Ferris, and David Orchard. Web Services Architecture [1]. W3C Working Group Note 11. 2004.

1 Web Services Architecture

A W3C document.
Working towards a standard.
Summarizes prevailing thought on Web Services
- What are the important parts?
- How to build them?
- How to fit parts together.
It provides a model (set of models) that describes how to build a web service architecture.

1.1 Standard Web Service

2 MetaModel

2.1 MetaModel Details

3 Message Oriented Model

Message Exchange Pattern is a template that describes a generic pattern for the exchange of message, akin to a FIPA IP.
Message Correlation associates a message with a context.
Message Header contains information that might have separate semantics from the message body.
Message Reliability is likelihood that both sender and receiver will have the same understanding of the delivery status.

4 Service Oriented Model

Choreography defines the sequence and conditions under which multiple cooperating independent agents exchange messages in order to perform a task to achieve a goal state.
Service represents a capability of performing tasks that represents a coherent functionality.
A service role is an intermediate abstraction between service and task. A given message that is received by a service may involve processing associated with several service roles.
A service task is an abstraction that encapsulates some intended effect of invoking a service.

5 Resource Oriented Model

Discovery is the act of locating a machine-processable description of a Web service-related resource
A discovery service is used to publish and search for descriptions meeting certain functional or semantic criteria.
Representations are data objects that reflect the state of a resource.
A resource description is a machine-processable description of a resource. Resource descriptions are used by and within discovery services to permit agents to discover the resource.

6 Policy Model

An audit guard is a mechanism used on behalf of an owner that monitors actions and agents to verify the satisfaction of obligations.
A domain defines the scope of applicability of policies.
A policy is a constraint on the behavior of agents as they perform actions or access resources. There are two kinds:
- When an agent has an obligation to perform some action, then it is required to do so.
- When an agent has permission to perform some action then it is expected that any attempt to perform the action will be successful.

1 Web Services Architecture