1. Chapter 4 Advanced Class Modeling

2. Advanced Class Modeling
Advanced Objects and Class Concepts
Association Ends
N-ary Associations
Aggregation
Abstract Class
Multiple Inheritance
Metadata
Reification
Constraints
Derived Data
Packages

3. 4.5 Abstract class
Abstract class is a class that has no direct instances but whose descendant classes have direct instance
Concrete Class is a class that is instantiable; it can have direct instances; can be leaf class in inheritance tree
Its good idea to avoid concrete superclass
All super classes are abstract and all leaf subclasses are concrete
Can eliminate concrete superclasses by introducing an “other subclass”
UML Notation: Class name in Italics
Keyword {abstract } before/after the name

4. 4.6 Multiple inheritance Permit a class to have more than one class
Advantage – Power in specifying classes & an increased opportunity for reuse
Disadvantage – Loss of conceptual & implementation simplicity
Concept – Generalization – Multiple Generalization
Language – Inheritance – Multiple Inheritance

5. 4.6.1 Kinds of Multiple Inheritance
Complete
Disjoint
Overlapping
Incomplete
UML Notation: Dotted Line cutting across the affected generalization with a constraint in {}
Refer Book for diagram

6. 4.6.2 multiple classification
One Instance to participate in two overlapping classes
One VTU Professor taking class in IIT
OO Languages handles it poorly, so workarounds will solve the same

7. 4.6.3 Workarounds Delegation using composition of Parts
Inherit the most important class and delegate the rest
Nested generalization
Issues to be considered
Superclass of equal importance – I
Dominant Superclass – II & III
Few Subclasses – III
Sequencing generalization sets - III
Large quantities of Code – Try to avoid - Dupe code & spoil OO Concepts
Identity – III Preserve

8. 4.7 Meta data Class Definition is a meta data Describes the data
Computer languages implements meta data heavily

9. 4.8 reification
Promotion of something that is not an object into an object
Useful to promote attributes, methods, constraints and control information into objects, so that it can be manipulated and described as data
Eg : Type cast in Programming lang
Association Class “Works For”

10. 4.9 Constraints
A boolean conditions involving model elements like objects, generalization set, links
Can be expressed using OCL
Constraints on objects
Constraints on Generalization Set
Semantics of generalization imply certain structural constraints – Disjoint; Overlapping; Complete; Incomplete
Constraints on Links
Multiplicity; Qualification; Association Class;
Constraints on Association End
Ordered; Subset; Bags; Sequence
Use of Constraint
Measuring the quality of the class model
“Good” Class Model Captures Important Constraints

11. 4.10 Derived Data
Function of one or more elements – derived attribute, association , classes
A class model should generally distinguish independent base attributes from dependent derived attribute
Use derived elements for implementation where they are compelling
UML Notation – A slash in the front of the element

12. 4.11 Packages Group of elements with a common theme
Packages are to organize large models so that the reader can understand portions of the model at a time, rather than having to deal with the whole model at once
Tips for devising packages
Carefully delineate each packages scope
Define each class in a single package