Attributes:
1. Relationship database does not directly support inheritance.
Attribute visibility, inclusion, static properties, and derived properties.
2. Operation definition of the responsibility.
Implementors operation, manager operation, help operation, and access operations.
Help operation: Mainly used in collaboration and sequence block diagrams
Operation version:
1. Implementor implements a certain business logic
Second, the operation of Manager constructor, deletion, and memory management
Third, Access makes other classes to browse or edit attributes
Fourth, Helper's dedicated and protection operations, other classes cannot be accessed.
Operation protocol:
Describe the operation of the client to the operation, and the order of operation.
