Chapter 1 thing View 9.1 Overview
Most of the content of the system model reflects the logic and design information of the system, and is independent of the final implementation unit of the system. However, for the purpose of reusability and operability, information on system implementation is also very important. UML uses two views to represent the implementation unit: the Implementation view and the deployment view.
The implementation view encapsulates reusable blocks in the system into alternative physical units called components. The implementation view uses the interfaces and dependencies between components to express the specific implementation of design elements (such as classes. A component is a reusable component at the system level.
The deployment view indicates the physical layout of computing resources (such as computers and their connections) during running. These running resources are called nodes. At runtime, nodes contain components and objects. The distribution of components and objects can be static, and they can also be migrated between nodes. If a component instance with dependency is deployed on different nodes, the deployment view shows the bottleneck during execution.
9.2 Components
A component is a physical implementation unit that defines good interfaces. It is a replaceable part of the system. Each component represents the implementation of specific classes in the system design. A well-defined component does not depend on other components directly, but on the interfaces supported by the component. In this case, a component in the system can be replaced by other components that support correct interfaces.
Components have interfaces they support and interfaces that need to be obtained from other components. An interface is an operation set supported by software or hardware. Using the named interface can avoid direct dependency between components in the system and facilitate replacement of new components. The component view shows the network structures of components that depend on each other. The component view can be expressed in two forms. One is a set of available components (Component Libraries) with dependencies. It is the physical organizational unit that constructs the system. It can also be represented as a configured system. The component used to build it has been selected. In this form, each component is connected to other components that provide services to it. These connections must comply with the interface requirements of the component.
The component is represented by a rectangle with two small rectangles on one side. It can be connected to a circle (9-1) representing the component interface with a solid line ).
A component diagram shows the dependencies between components (9-2 ). Each component implements (supports) Some interfaces and uses other interfaces. If the dependency between components is related to interfaces, the components can be replaced by other components with the same interfaces.
Figure 9-1 with interface components
Figure 9-2 component Diagram
9.3 nodes
A node is a physical object that represents the runtime of computing resources. It usually has memory and processing capabilities. A node may have a constructor used to identify various resources, such as CPU, device, and memory. Nodes can contain objects and component instances.
Figure 9-3 Deployment
Nodes are represented by cubes with node names. They can be classified (optional) (9-3 ).
The association between nodes represents the communication path. Association is used to identify the constructors of different paths.
Nodes also have a general relationship, linking the general description of nodes with specific special cases.
Objects in a node are represented by object symbols nested in the node symbol. If this is inconvenient, the object symbol can contain the location tag that represents the name of the node where it is located. Migration of objects or component instances between nodes can also be expressed.
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