Client/Server Computing and Middleware

Client/server computing enables sites to exploit the power of networked computing systems. Heterogeneous in nature, client/server architecture divides application components such as screen formatting, program logic, and data access between several networked processors to exploit unique characteristics in each environment:

• A client, such as FOCUS for Mainframe, typically builds a request and specifies a report layout.
• A remote server, or back-end, then performs data selection and handles data integration and aggregation.

By enabling numerous front-end tools to share centralized back-end services, client/server computing introduces the concept of interoperability. Seamless integration of the front- and back-end processes is accomplished through a new layer of systems software, called middleware, which provides interoperability by delivering transparent data transmission and translation services between physically linked processors.

Middleware insulates end users and application developers from dealing with the complexities and incompatibilities of networked proprietary computing environments. This is accomplished through three components:

• Application Programming Interface (API). This client component, built into FOCUS for Mainframe, requests remote services using SQL requests.
• Database Server or Gateway. This back-end server or gateway translates remote requests into formats suitable for the specified target environment and executes them.
• Network Communications. Network communication services provide protocol translation services, masking incompatibilities between proprietary networks and interconnected systems.

The communications system and protocol subsystem, which together make up Network Communications, shield the API and server from details of various communications protocol syntaxes. Each protocol subsystem is a platform specific interface to a supported communications protocol. Together, these components enable applications to send requests to a variety of servers and to receive answers (data or messages) in return.