Use an Acknowledgment to Check Receipt
Use the explicit acknowledgment as receipt evidence and keep missing responses uncertain.
About 18 minutes, plus any extended practice
Supplied materials
- Paper and pencil; answers may also be spoken or typed.
- All cases, labels, numbers and rules are supplied on this page. No real account, private information or purchase is needed.
Learn the idea
An acknowledgment is a response saying that a stated message or part was received. No response does not prove the destination never received it; the response itself may be delayed or lost. The paper log distinguishes confirmed receipt from an unknown outcome.
Compare the target message ID with any acknowledgment ID. Distinguish no response recorded from a response for a different message; either leaves target receipt unknown. Only a matching acknowledgment confirms the stated receipt.
Use this supplied case: Message 7 sent; acknowledgment 7 arrives. Classify the log evidence. Use the details in this example. Say which detail helped you choose. This pretend example does not tell us how every real system works.
- Follow the worked example one step at a time. Say or draw what happens.
- Use the explicit acknowledgment as receipt evidence and keep missing responses uncertain.
- Say which detail makes the example answer fit. Pick another answer and say why it does not fit.
- Try the question and practice questions. Read the rule again if your answer does not match the explanation.
See the method in action
Message 7 is sent and acknowledgment 7 arrives. Compare IDs: 7=7, so the response confirms receipt of message 7. In a different log, message 31 is sent and acknowledgment 30 arrives. The response exists, but 31≠30, so it confirms another message and leaves 31 unconfirmed. If there were no response, the log would show a missing acknowledgment, not definite nonreceipt; the message or response could be delayed.
Check your reasoning
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Helpful tips
- Use the explicit acknowledgment as receipt evidence and keep missing responses uncertain.
- Sending a message is different from confirming its receipt.
See the answer and explanation
Sent with no acknowledgment recorded; receipt remains unknown
Read the sent message ID and any acknowledgment ID separately. Message 8 sent; no response in log. Which specific sending-and-acknowledgment condition does this log show? This supports: Sent with no acknowledgment recorded; receipt remains unknown. A response for another message does not confirm the target, and no response does not prove nonreceipt.
Take it further
Message 21 is sent; acknowledgment 20 arrives. Expected: receipt of 21 remains unconfirmed because the response identifies another message.
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More practice: try new cases
Choose an answer for each problem. Explain your method on paper, then use the feedback to decide what to revisit.
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Check the subject sources
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