Web services Guide
The VisualAge Web services architecture is a framework that enables
e-business services to be described, published, discovered, and invoked
dynamically in a distributed computing environment.
Web services:
Web services are self-contained, modular applications that can be:
- Described using a service description language. The
description language that is being endorsed by IBM is WSDL (Web services
Description Language).
- Published by registering their descriptions and use policies
with a well-known registry. The registry being endorsed by IBM is the
UDDI (Universal Description, Discovery and Integration) registry.
- Found by sending queries to UDDI registry and receiving the
binding details of the service(s) that fit the parameters of the query.
- Bound by using the information contained in the service
description to create a callable service instance or proxy.
- Invoked over a network by using the information contained in
the binding details of the service description.
- Composed with other services into new services and
applications.

VisualAge Web services have focused on enhancing the ability of a Web
service to be found, bound, invoked and composed, which provides a robust and
extensible Web services platform that allows users to maintain the object
paradigm when building Web services in Smalltalk.
Web services Components:
- Service This is the application being provided for use by
requesters that fit the prerequisites specified by the Service
Provider. Its implementation is deployed on a network accessible
platform. It is described through a service description
language. Its description and access policies have been published to a
registry.
- Service Provider From a business perspective, this is the owner
of the service. From an architectural perspective, this is the platform
that provides access to the service.
- Service Registry This is a searchable repository of service
descriptions where service providers publish their services and service
requesters find services and obtain binding information for services.
- Service Requestor From a business perspective, this is the
business that requires certain function to be fulfilled. From an
architectural perspective, this is the application or client that is looking
for and invoking a service.
Web services Operations:
- Publish/Unpublish Service Providers advertise (publish) the
availability of their e-business service to one or more service registries, or
remove the advertisement of (unpublish) their service.
- Find Service Requestors interact with one or more service
registries to discover a set of services that it can interact with to provide
a solution.
- Bind Service Requestors negotiate with Service Providers to
access and invoke e-business services.
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