Unified Modeling Language

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Introduction
The Unified Modeling Language (UML) emerged in response to a need for a notation (a visual language) that can express the behaviors of today’s interactive computing systems and that can guide in constructing them. In the UML framework, software design entails building an object-oriented representation of a system, as well as of its environment, e.g. its users (modeled as actors).
Interactive systems such as modeled with UML represent a new paradigm in computation that inherently cannot be modeled using traditional, or algorithmic, tools. At the heart of the new computing paradigm is the notion that a system’s job is not to transform a single static input to an output, but rather to provide an ongoing service [We2]. The service-providing nature of present-day systems was specifically noted by the Object Management Group (OMG) in defining the UML standard [OMG1].
When a system is viewed as a service provider, the interaction between the system and its environment becomes an integral part of the computing process. UML presents a uniform domain-independent framework for modeling the different interactions present in today’s systems: interactions among objects or software components, interactions between users and applications, interactions over networks (including the Internet), and interactions among embedded devices.