2. Types of relationships
• Association
• Super-sub structure (generalization
hierarchy)
• Aggregation and part of a structure
3. Association
• Represents physical or conceptual
connection between 2 or more objects
• Binary association
– Line connecting 2 classes
• Ternary and higher order association
– Diamond connecting to a class symbol by line
• Association name is written above or
below the name
• Includes name of the role
5. Identifying association
• Begins by analyzing the interaction among
classes
• Ask following questions
– Is the class capable of fulfilling the required task by
itself
– If not, what does it need
– From what other class can it acquire what it needs
• Guideline
– Dependency between 2 or more classes
• Association corresponds to verb or prepositional phrase
– Reference from one class to another
• Implicit or taken from knowledge
6. Common association pattern
• Location association
– Ex: next to, part of , contained in
• Communication association
– Ex :talk to, order to
operator
customer
order
7. Eliminate unnecessary association
• Implementation association
– Defer implementation specific association to design phase
– Not concerned about relationship among business objects
• Ternary association
– Complicate the representation
– Req
• Restate ternary association to binary association
• Directed actions or derived association
– Can be defined in terms of other association
– Leads to redundancy
– Ex:
Grant parent of
raman abi
parent of parent of
raman murugan abi
8. Super-sub class relationships
• Generalization hierarchy
• Represents the inheritance relationship bw
related class
• Parent class
– Super class
– Ancestor
9. Guidelines to identify
Super-sub class relationships (cont..)
– Top down
• Look for noun phrases composed of various adjectives in a
class name
– Ex: youth member, adult member
– Bottom up
• Look for classes with similar attribute and methods
– Reusability
• Move attribute and behavior as high as possible in the
hierarchy
– Multiple inheritance
• Avoid excessive use of multiple inheritance. Leads to
complications
10. A part of realtionships-aggregation
• Represents a situation where a class
consists of several component classes
• Properties
– Transitivity
• A is part of B , B is part of C, then A is part of C
– Antisymmetry
• A is part of B, but B is not part of A
11. Representation of aggregation
• Container and collection
– hollow diamond
• Composition
– Solid diamond
– Ex:
• Car and its parts
12. A part of relationship pattern
• Assembly
– French onion soup is an assembly of inion ,
butter, floor,bread
• Container house
• Collection furniture appliances
– Team and player
