loose coupling

Refers to hardware and software components that interact when necessary, but remain uncoupled from each other. For example, computers in a network are loosely coupled. When the user's client machine requires data from the server, it sends a request to the server. Otherwise, it performs work independently. In a loosely-coupled multiprocessing environment, where several computers share the workload, a machine can be added and replaced without shutting down the entire system.

Software Loose Coupling
Loosely-coupled software means routines (modules, programs) are called by an application and executed as needed. For example, Web services employ loose coupling. When a function is required, the appropriate Web service module is executed. Loosely-coupled software often refers to programs with standard interfaces that serve multiple computing environments. Contrast with tight coupling. See Web services.