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Unt 3 attributes, methods, relationships-1


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Unt 3 attributes, methods, relationships-1

  1. 1. Identifying objectrelationships ,attributes , methods,
  2. 2. Types of relationships• Association• Super-sub structure (generalization hierarchy)• Aggregation and part of a structure
  3. 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. 4. Cont..• Identifying association• Common association pattern• Eliminating unnecessary association
  5. 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. 6. Common association pattern• Location association – Ex: next to, part of , contained in• Communication association – Ex :talk to, order to operator customer order
  7. 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. 8. Super-sub class relationships• Generalization hierarchy• Represents the inheritance relationship bw related class• Parent class – Super class – Ancestor
  9. 9. Guidelines to identifySuper-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. 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. 11. Representation of aggregation• Container and collection – hollow diamond• Composition – Solid diamond – Ex: • Car and its parts
  12. 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