A\u00a0component<\/b>\u00a0in the\u00a0Unified Modeling Language<\/a>\u00a0represents a\u00a0modular<\/a>\u00a0part of a\u00a0system<\/a>\u00a0that\u00a0encapsulates<\/a>\u00a0the\u00a0state<\/a>\u00a0and\u00a0behavior<\/a>\u00a0of a number of\u00a0classifiers<\/a>. Its behavior is defined in terms of\u00a0provided<\/i>\u00a0and\u00a0required<\/i>\u00a0interfaces<\/a>, <\/sup>is\u00a0self-contained<\/a>, and\u00a0substitutable<\/a>. A number of UML standard\u00a0stereotypes<\/a>\u00a0exist that apply to components.<\/sup><\/p>\n A component has an external and internal view, also known as “black-box<\/a>” and\u00a0“white-box”<\/a>, respectively. In its external view, there are public properties and operations. For its internal view, there are private properties and realizing classifiers and shows how external behavior is realized internally.<\/sup><\/p>\n A component may be replaced at\u00a0design time or run-time<\/a>\u00a0by another if and only if their provided and required interfaces are identical. This idea is the underpinning for the\u00a0plug-and-play<\/a>\u00a0capability of\u00a0component-based<\/a>\u00a0systems and promotes\u00a0software reuse<\/a>. <\/sup>Larger pieces of a\u00a0system<\/a>‘s functionality may be assembled by reusing components as parts in an encompassing component or assembly of components, and wiring together their required and provided interfaces.<\/sup><\/p>\n A component acts like a\u00a0package<\/a>\u00a0for all model elements that are involved in or related to its definition, which should be either owned or imported explicitly. Typically the classifiers related to a component are owned by it.<\/sup><\/p>\n Components of a system are modeled by means of\u00a0component diagrams<\/a>\u00a0throughout the\u00a0development life cycle<\/a>\u00a0and successively refined into deployment and run-time.<\/sup><\/p>\n In diagrams, components are shown as a\u00a0rectangle<\/a>\u00a0with the keyword \u00abcomponent\u00bb. Optionally, in the right hand corner a component icon can be displayed. This is a rectangle with two smaller rectangles protruding from its left hand side. If the icon symbol is shown, the keyword \u00abcomponent\u00bb may be hidden as seen to the side.<\/p>\n In\u00a0Unified Modeling Language<\/a>\u00a0(UML), a\u00a0component diagram<\/b>\u00a0depicts how\u00a0components<\/a>\u00a0are wired together to form larger components or\u00a0software systems<\/a>. They are used to illustrate the structure of arbitrarily complex systems.<\/p>\n A component diagram allows verification that a system’s required functionality is acceptable. These diagrams are also used as a communication tool between the developer and stakeholders of the system. Programmers and developers use the diagrams to formalize a roadmap for the implementation, allowing for better decision-making about task assignment or needed skill improvements. System administrators can use component diagrams to plan ahead, using the view of the logical software components and their relationships on the system.<\/p>\n The component diagram extends the information given in a component notation element. One way of illustrating the provided and required\u00a0interfaces<\/a> by the specified component is in the form of a rectangular compartment attached to the component element.\u00a0Another accepted way of presenting the interfaces is to use the\u00a0ball-and-socket graphic convention<\/a>. A\u00a0provided<\/i>\u00a0dependency from a component to an interface is illustrated with a solid line to the component using the interface from a “lollipop”, or ball, labelled with the name of the interface. A\u00a0required<\/i>\u00a0usage dependency from a component to an interface is illustrated by a half-circle, or socket, labelled with the name of the interface, attached by a solid line to the component that requires this interface. Inherited interfaces may be shown with a lollipop, preceding the name label with a\u00a0caret<\/a>\u00a0symbol. To illustrate dependencies between the two, use a solid line with a plain arrowhead joining the socket to the lollipop.<\/p>\n","protected":false},"excerpt":{"rendered":"Component Diagrams<\/h2>\n
Overview<\/span><\/h3>\n
Diagram elements<\/span><\/h3>\n