3. Web Services – Architecture

Web Services – Architecture:

There are two ways to view the web service architecture.

·         The first is to examine the individual roles of each web service actor.

·         The second is to examine the emerging web service protocol stack.

1. Web Service Roles

There are three major roles within the web service architecture:

• Service provider:

This is the provider of the web service. The service provider implements the service and makes it available on the Internet.

• Service requestor

This is any consumer of the web service. The requestor utilizes an existing web service by opening a network connection and sending an XML request.

• Service registry

This is a logically centralized directory of services. The registry provides a central place where developers can publish new services or find existing ones. It therefore serves as a centralized clearinghouse for companies and their services.

---

2. Web Service Protocol Stack

A second option for viewing the web service architecture is to examine the emerging web service protocol stack. The stack is still evolving, but currently has four main layers.

• Service transport

This layer is responsible for transporting messages between applications. Currently, this layer includes hypertext transfer protocol (HTTP), Simple Mail Transfer Protocol (SMTP), file transfer protocol (FTP), and newer protocols, such as Blocks Extensible Exchange Protocol (BEEP).

• XML messaging

This layer is responsible for encoding messages in a common XML format so that messages can be understood at either end. Currently, this layer includes XML-RPC and SOAP.

• Service description

This layer is responsible for describing the public interface to a specific web service. Currently, service description is handled via the Web Service Description Language (WSDL).

• Service discovery

This layer is responsible for centralizing services into a common registry, and providing easy publish/find functionality. Currently, service discovery is handled via Universal Description, Discovery, and Integration (UDDI).

As web services evolve, additional layers may be added, and additional technologies may be added to each layer.