Classes in UML

• Most important building block of any OO system
• Naming
• Should be named in the vocabulary of the problem domain
• Typically singular noun starting with a capital letter
• Diagram – Rectangle divided in to name, attributes, operations, and sometimes responsibilities
• Public – can be used by the class’s operations and by any one outside the class
• Protected – can be used by the class’s operations and any derived class
• Private – can be used by the class’s operations only

• Well Structured Classes
• Provide a crisp abstraction of an object in the problem domain
• Embody a small, well-defined set of responsibilities
• Separate specification and implementation
• Are simple but extensible

• When you draw a class in UML
• Show only those properties that are important to understand the object in its context
• Group attributes by category
• Show related classes in the same diagram

Class Diagram Example: