Common Mechanisms of UML

Modeling Webs of Relationships 

When you model these webs of relationships: 

• From use cases and scenarios, discover the relationships among a set of abstractions 
• The structural relationships are the most obvious and tangible. Start with these 
• Then, discover specialization/generalization relationships and use multiple inheritance, only when absolutely necessary 
• Dependencies come later which is not so obvious a form of semantic connection 
• For each type of relationship, begin with its basic form and apply advanced features, only as needed to express the objective 
• It may not aid better understanding to model all relationships among a set of abstractions in a single diagram or view 
• Instead, distribute them to different views of the system showing relevant relationships in individual diagrams

Interfaces, Types and Roles
Interface 

• An interface is a collection of operations that are used to specify a service of a class or component 
• An interface does not specify any structure (attributes) nor any implementation of the operations in the collection 
• A line between the specifications of what an abstraction does and the implementation of how that abstraction does it is defined by an interface 

Relationships between Interfaces and Other Classifiers 

• A class can realize one or more interfaces 
• An interface can be realized by one or more interfaces 
• A class can depend on an interface

Inheritance Relationship between Interfaces

Interface for Role

A package is a general-purpose mechanism for organizing elements into groups.

Owned Elements 

• A package can own other elements, even other packages 
• Every element is uniquely owned by exactly one package 
• A package forms a name space. If the two elements are owned by two different packages then it may have the same name 

Example:
BuyerPackage::Information class
SellerPackage::Information class

• Elements of different kinds may have the same name 

Example:
BuyerPackage::Information class BuyerPackage::Information component

• Path names in nested packages 

Example:
CustomerPackage::BuyerPackage::Information class