UML Diagrams: Part 2

UML (Unified Modeling Language) is a standardized general-purpose modeling language in the field of object-oriented software engineering .It is a visual language for specifying, constructing, and documenting the artifacts of systems. The UML offers a standard way to write a system's blueprints, including conceptual things such as business processes and system functions as well as concrete things such as programming language statements, database schemas, and reusable software components.

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7. Sequence Diagram:

UML sequence diagrams are used to represent or model the flow of messages, events and actions between the objects or components of a system. Time is represented in the vertical direction showing the sequence of interactions of the header elements, which are displayed horizontally at the top of the diagram.

Sequence Diagrams are used primarily to design, document and validate the architecture, interfaces and logic of the system by describing the sequence of actions that need to be performed to complete a task or scenario. UML sequence diagrams are useful design tools because they provide a dynamic view of the system behavior which can be difficult to extract from static diagrams or specifications.



8. Time Diagram:

Timing diagrams are UML interaction diagrams used to show interactions when a primary purpose of the diagram is to reason about time. Timing diagrams focus on conditions changing within and among lifelines along a linear time axis. Timing diagrams describe behavior of both individual classifiers and interactions of classifiers, focusing attention on time of events causing changes in the modeled conditions of the lifelines.

The following nodes and edges are typically drawn in a UML timing diagram: lifeline, state or condition timeline, destruction event, duration constraint, time constraint.



9. UseCase Diagram:

Use cases are used during the analysis phase of a project to identify and partition system functionality. They separate the system into actors and use cases.

Actors represent roles that can are played by users of the system. Those users can be humans, other computers, pieces of hardware, or even other software systems. The only criterion is that they must be external to the part of the system being partitioned into use cases. They must supply stimuli to that part of the system, and the must receive outputs from it.

Use cases describe the behavior of the system when one of these actors sends one particular stimulus. This behavior is described textually. It describes the nature of the stimulus that triggers the use case; the inputs from and outputs to other actors, and the behaviors that convert the inputs to the outputs. The text of the use case also usually describes everything that can go wrong during the course of the specified behavior, and what remedial action the system will take.



10. Deployment Diagram:

The deployment diagram shows how a system will be physically deployed in the hardware environment. Its purpose is to show where the different components of the system will physically run and how they will communicate with each other. Since the diagram models the physical runtime, a system's production staff will make considerable use of this diagram.
 
The notation in a deployment diagram includes the notation elements used in a component diagram, with a couple of additions, including the concept of a node. A node represents either a physical machine or a virtual machine node (e.g., a mainframe node). To model a node, simply draw a three-dimensional cube with the name of the node at the top of the cube.



11. State Machine Diagram:

UML state machine diagrams depict the various states that an object may be in and the transitions between those states. In fact, in other modeling languages, it is common for this type of a diagram to be called a state-transition diagram or even simply a state diagram. A state represents a stage in the behavior pattern of an object, and like UML activity diagrams it is possible to have initial states and final states. An initial state, also called a creation state, is the one that an object is in when it is first created, whereas a final state is one in which no transitions lead out of. A transition is a progression from one state to another and will be triggered by an event that is either internal or external to the object.



12. Communication Diagram:

Communication diagrams show the message flow between objects in an OO application and also imply the basic associations (relationships) between classes. Similar to Sequence Diagram, the Communication Diagram is also used to model the dynamic behavior of the use case. When compare to Sequence Diagram, the Communication Diagram is more focused on showing the collaboration of objects rather than the time sequence.



13. Interaction Overview Diagram:

The Interaction Overview Diagram focuses on the overview of the flow of control of the interactions. It is a variant of the Activity Diagram where the nodes are the interactions or interaction occurrences. The Interaction Overview Diagram describes the interactions where messages and lifelines are hidden. You can link up the "real" diagrams and achieve high degree navigability between diagrams inside the Interaction Overview Diagram.