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A use case is a list of actions or event steps that typically define the interaction between an actor (called an actor in Unified Modeling Language (UML)) and a system to achieve a goal. Actors can be people or other external systems. In systems engineering, use cases are used at a higher level than in software engineering and usually represent task or stakeholder goals.

A use case diagram is a UML diagram that enables you to model system functions (i.e., goals) and the actors that interact with those functions. You can draw use case diagrams in Visual Paradigm or use the Event Flow Editor to document use case usage scenarios. On this page, you will see how to draw use case diagrams with UML tools.

In the area of software testing, “use case” and “test case” are the most critical and closely interrelated terms, but they are quite different. A use case tells us how a system will behave or perform a given task under given conditions. A test case contains the actual test data, the instruction set of the system, and the expected results of the interaction with the system.

Use case diagrams help stakeholders to understand the nature and scope of the business area or the system under development, thus, use case modeling is generally regarded as an excellent technique for capturing the functional requirements of a system. They can be served as the basis for the estimating, scheduling, and validating effort.

Activity Diagrams describe how activities are coordinated to provide a service which can be at different levels of abstraction. Typically, an event needs to be achieved by some operation, particularly where the operation is intended to achieve a number of different things that require coordination, or how the events in a single use case relate to one another, in particular, use cases where activities may overlap and require coordination. It is also suitable for modeling how a collection of use cases coordinate to create a workflow for an organization.