Compare inheritance with composition
See this course’s project requirements
An original library-room booking simulation using independent objects, invariants, composition and an event history.
Keep your working files in your own notebook or software. Save a private description, checklist, and work link in My Proof.
What to include
- A room-state contract with 10:00 mapped to 3.
- An independent-instance check with unchanged B.
- A rejection record with unchanged booking state.
- A composed booking trace with no event for an unknown room.
- A composition design note with responsibility boundaries.
- A tested booking model with independent state and honest rejection evidence.
Review and revise
Use these criteria to check your work and choose what to improve.
- The implementation or declared simulation follows the supplied contract and retains inspectable original inputs.
- Normal, boundary and rejected cases are recorded with expected versus observed results.
- The changed case has a correct explanation and does not rely on hidden state.
- The project includes source, outputs, instructions and honest tool, privacy and verification limits.
Want more background?
The idea in everyday life
Someone proposes class Scheduler(Room). Another proposes Scheduler holding a dictionary of Room instances.
Use an is-a relationship for inheritance and a has-a relationship for composition. This scheduler is not a room: it manages several rooms. Keeping policies in the appropriate object prevents duplicated capacity checks.
Compare inheritance with composition — original worked practice
Use an is-a relationship for inheritance and a has-a relationship for composition. This scheduler is not a room: it manages several rooms. Keeping policies in the appropriate object prevents duplicated capacity checks.
Someone proposes class Scheduler(Room). Another proposes Scheduler holding a dictionary of Room instances.
1. Step 1
Write each object’s role in one sentence.
You should see: A Room holds bookings; a Scheduler coordinates rooms.
This keeps the rule and its observable result together.
2. Step 2
Test whether a scheduler can stand in for one room.
You should see: It has no single room capacity or booking slot set.
This keeps the rule and its observable result together.
3. Step 3
Choose composition and identify delegated rules.
You should see: Room validates its bookings; Scheduler chooses a room and records events.
This keeps the rule and its observable result together.
4. Step 4
Draw the containment relationship and justify it.
You should see: A composition design note with responsibility boundaries.
This keeps the rule and its observable result together.
What to finish
A composition design note with responsibility boundaries.
Watch for this
Using inheritance solely to share a helper when the scheduler actually contains separate rooms.
How can I tell I understand it?
Explain and demonstrate the required distinction: Use an is-a relationship for inheritance and a has-a relationship for composition. This scheduler is not a room: it manages several rooms. Keeping policies in the appropriate object prevents duplicated capacity checks. Show a changed input and the expected result without weakening this contract.
Quick knowledge check
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Source & access notes · checked 2026-10-01
Relevant documented module/API behavior inspected during expansion authoring; actual execution evidence is recorded separately. No grant eligibility is established.
Access: Official page retrieved with the web reader on 2026-10-01. Documentation reading does not certify execution in every native tool or browser.
Reuse: Original local practice files, fictional data, worked examples and questions. Concepts paraphrased and linked; source exercises are not copied.
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