Things
Four Types
Structural things -- The nouns of UML models. These represent elements that are conceptual or physical. There are seven kinds of structural things: Class, Interface, Collaboration, Use Case, Active Class, Component, and Node. (See the examples below.)
Behavioral things -- Dynamic parts of UML models. The verbs which represent behavior over time and space. There are two kinds of behavioral things: Interaction, and State Machine. (See the examples below.)
Grouping things -- Organizational parts of UML. These are boxes into which models can be decomposed. There is only one kind of grouping thing, the Package. (See the examples below.)
Annotational things -- Explanatory parts of UML. Used to describe, illuminate, and remark any element of a model. There is only one kind of annotational thing, the Note. (See the examples below.)
Relationships
Four Types
Dependency -- A semantic relationship in which a change on one thing (the independent thing) may cause changes in the other thing (the dependent thing). (See the examples below.)
Association -- A structural relationship describing links between objects. May also include labels to indicate number and role of the links. In the example shown below there may be any number of employees (*) each of which has 0 or 1 employer. (See the examples below.)
Generalization -- A specialization/generalization relationship. Simply put this describes the relationship of a parent class (generalization) to its subclasses (specializations). (See the examples below.)
Realization -- Defines a relationship in which one class specifies something that another class will perform. Example: The relationship between an interface and the class that realizes or executes that interface. (See the examples below.)
Diagrams
Nine Types
Class Diagram -- A set of classes, interfaces, and collaborations and their relationships. Most often found in modeling Object Oriented systems. (See the examples below.)
Object Diagram -- A set of objects and their relationships. Represents static instances of things found in class diagrams. (See the examples below.)
Use Case Diagram -- A set of Use Cases and actors. (See the examples below.)
Sequence Diagram -- An interactive diagram (set of objects, relationships, and messages that may be exchanged) emphasizing the time-ordering of messages. (See the examples below.)
Collaboration Diagram -- An interaction diagram emphasizes the structural organization of the objects that send and receive messages. (See the examples below.)
Statechart Diagram -- Shows a state machine with states, transitions, events, and activities. (See the examples below.)
Activity Diagram -- Special type of statechart diagram that shows the flow from activity to activity within a system. (See the examples below.)
Component Diagram -- Shows the organizations and dependencies among a set of components. (See the examples below.)
Deployment Diagram -- Shows the configuration of run-time processing nodes and the components that are part of them. (See the examples below.)