Identify state and allowed behavior
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
Room A holds 4 people. It has no bookings. A request asks for 3 people at 10:00.
An object joins state with operations that preserve its rules. A room name and capacity describe the object; a booking operation changes only the booking state when its preconditions hold.
Identify state and allowed behavior — original worked practice
An object joins state with operations that preserve its rules. A room name and capacity describe the object; a booking operation changes only the booking state when its preconditions hold.
Room A holds 4 people. It has no bookings. A request asks for 3 people at 10:00.
1. Step 1
List fixed and changing fields.
You should see: name A/capacity 4 are fixed in this case; bookings can change.
This keeps the rule and its observable result together.
2. Step 2
Write the permitted party-size rule.
You should see: People must be an integer between 1 and 4 inclusive.
This keeps the rule and its observable result together.
3. Step 3
State the slot uniqueness rule.
You should see: A slot may appear only once in a room’s bookings.
This keeps the rule and its observable result together.
4. Step 4
Define the accepted request and resulting state.
You should see: A room-state contract with 10:00 mapped to 3.
This keeps the rule and its observable result together.
What to finish
A room-state contract with 10:00 mapped to 3.
Watch for this
Putting every booking in a single global collection rather than locating the state owned by each room.
How can I tell I understand it?
Explain and demonstrate the required distinction: An object joins state with operations that preserve its rules. A room name and capacity describe the object; a booking operation changes only the booking state when its preconditions hold. Show a changed input and the expected result without weakening this contract.
Quick knowledge check
Answer all 3 questions. Get at least 2 right and the lesson completes automatically.
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Answer all 3 questions above and get at least 2 right. You can review the explanations and try again.
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Sources and further reading
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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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