Unt 3 attributes, methods, relationships-1
- 1. Identifying object relationships ,attributes , methods,
- 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
- 4. Cont.. • Identifying association • Common association pattern • Eliminating unnecessary association
- 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