Web Services architecture

Web Services architecture basically consists of Web services technologies that are capable of: exchanging messages, describing Web services, and publishing and discovering Web service descriptions. To accomplish these ends, interactions involving publish, find and bind operations must occur between the following three roles:

The Service Provider typically hosts an implementation of a web service (a network-accessible software module) and provides a description of the web service. The service description includes data type and structure information, identifies message exchange patterns, and contains the address of the Service Provider. The Service Provider then publishes the service description to a Service Registry.

The Service Registry is a searchable set of service descriptions where Service Providers publish their service descriptions. The Service Registry acts as a discovery agency that provides, as well as makes discoverable, service descriptions.

The Service Requester interacts with the Service Registry to find required services. A service is invoked after the description is found, since the service description is required to establish a binding. Once found, the Service Requester interacts with the Service Provider, using the binding details in the service description to locate, contact, and invoke the service. This bind creates an association between them that ensures web service implementation.

In this architecture, a service is an implementation of a Web service; that is a software module deployed on network-accessible platform provided by the Service Provider. A service description contains details of the service, including data types, operations, binding information and its network location (as well as the metadata describing this service). The service description must include sufficient information for a service requester to access the service it describes. This architecture is shown in the following figure, and described in Table 3.

Table 3. Fundamental roles in Web Services
Service role	Description
Service Provider	The Service Provider publishes a service description to a Service Registry. From a business perspective, the Service Provider is the owner of the service. From an architectural perspective, it is the platform that hosts access to the service.
Service Registry	The service registry provides a searchable set of services, enabling users to find businesses worldwide that offer the exact products and services that are required.
Service Requester	From a business perspective, a service requester is the consumer of a service. From an architectural perspective, it is an application that searches for a service description that matches its request via the Service Registry, and then invokes or initiates an interaction with the service. When the request and matching description bind, the application connects to a Web service at a particular Web location and starts interacting with it.