On what basis does algorithmic decomposition break up a system, compared with OO decomposition?

Algorithmic uses steps/functions (what happens next); OO uses objects/classes (who is responsible for what)

Algorithmic uses objects/nouns; OO uses steps/verbs

Algorithmic uses inheritance; OO uses flowcharts only

Why is change easier in OO decomposition?

Data is encapsulated inside objects, so a change is localised in a class

Functions are reused everywhere

What does the 'is-a' hierarchy contribute to decomposition?

Common structure and behaviour sit at the top and are inherited, so they are written once

Which is an example of the 'part-of' hierarchy?

A Computer has a CPU and Disk (aggregation)

Circle.draw() versus Square.draw()

A DFD process calls another process

2070 Bhadra · 6+4 marks

Algorithmic vs object-oriented decomposition

Short answer

Algorithmic decomposition breaks a system into functions and processes, keeping data separate and often global, making data changes propagate. Object-oriented decomposition breaks it into objects encapsulating data and behavior, localizing change. Hierarchy (is-a and part-of) organizes classes, enabling reuse, polymorphism, and manageable complexity.

What are the differences between algorithmic decomposition and object-oriented decomposition in the process of systems analysis for a complex system? What is the role of hierarchy, another feature of object-orientation, in such decomposition process?

Decomposition means breaking a complex system into smaller, manageable parts. There are two approaches: algorithmic (functional) and object-oriented.

Differences

Point	Algorithmic decomposition	Object-oriented decomposition
Basis	Steps/functions (verbs)	Objects/classes (nouns)
Question asked	"What happens next?"	"Who is responsible for what?"
Focus	Process/algorithm	Entities with state and behaviour
Data	Shared, separate from functions	Encapsulated inside objects
Model	DFD, structure chart, flowchart	Class, sequence, use case diagrams
Change	A data change affects many functions	Change is localised in a class
Reuse	Reuse of functions	Reuse of classes, inheritance
Complexity handling	Weak for large systems	Better: models real-world entities

Example (library system):

Algorithmic: search_book() -> issue_book() -> calculate_fine() -> return_book().
Object-oriented: classes Book, Member, Librarian, Loan, each with its own data and operations that collaborate.

 Algorithmic          Object-oriented
 -----------          ---------------
  Main                 Member --- Loan --- Book
  +- Issue                \         |
  +- Return                +- Librarian
  +- Fine

Role of hierarchy

Hierarchy is the ranking or ordering of abstractions, and is the main tool that makes object-oriented decomposition manageable. Booch identifies two kinds:

"is-a" hierarchy (inheritance): Student and Teacher are kinds of Person. Common structure and behaviour sit at the top and are inherited, so they are written once.
"part-of" hierarchy (aggregation): a Library has Books, Members; a Computer has a CPU, Disk. A complex object is understood as an assembly of simpler parts.

Hierarchy therefore organises the classes found during decomposition into layers, reduces duplication, allows polymorphism, and lets the analyst study the system at several levels of detail.

✓ Answer checked by Claude Opus 5.5 (high effort)

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