Chapter 12 — A missing row is not a free room
Lesson map
Lesson 12 published. Map, example, EX028.
flowchart TD
Q["The question names one room and one start"] --> M{"A printed row has that room and that start?"}
M -->|Yes| T["Read the status on that row"]
M -->|No| S["This page is silent"]
S --> P["Leave the request pending"]
P --> F["Do not call the room free"]
F --> L["Leave the Chapter 4 ALLOW label on the old log"]
A match reads a row. A miss reads nothing. The miss does not invent availability.
Logical drawing
named page: two printed rows, both Room 2
Room 2 at 15:00 -> SYN-002 matches -> taken
Room 2 at 14:00 -> SYN-001 matches -> taken
Room 4 at 15:00 -> no row matches -> silent
|
+-- silent means the page does not answer
+-- silent does not mean the room is free
+-- ALLOW on the 09:00 log is not a row here
+-- do not pencil a Room 4 line onto the page
Learning outcomes
After this chapter, you should be able to:
- Match a room-and-start question to a row on the named 11:40 page.
- Treat a question with no matching row as silence, not as a free room.
- Leave the Chapter 4 ALLOW label and the printed census on the 09:00 log.
12.1 Authority is not the same claim as completeness
Chapter 11 used the named page for a question the page can answer. SYN-002 prints Room 2 at 15:00, so that slot is taken. A new resident question now asks for Room 4 at 15:00. The same page is still on the table. Its two rows are still the whole page. Neither row says Room 4.
Naming gave permission to read this object in this exercise. It did not say that two rows are every booking in the building. Those are separate claims. The first claim is about authority. The second would be about completeness, and the owner has not made it.
Search the page by the pair the resident asked for. Room and start must both match. SYN-001 matches Room 2 at 14:00, so that slot is taken for its own question. It does not answer Room 4. SYN-002 matches Room 2 at 15:00. It also does not answer Room 4. After both rows are checked, the matching count for Room 4 at 15:00 is zero. Zero matches is silence. Silence supports neither "taken" nor "free."
The spoken reply is therefore limited: "This page does not list Room 4 at 15:00, so I cannot answer from it." Staff record the request as pending. They do not offer the room.
12.2 Worked example
A classmate treats the old ALLOW label as if it were the missing row. In Chapter 4, ALLOW was the label for one logged action: a Room 4 question compared with the 09:00 printout. The reason on that run was that the printout's table had no later booking for the slot. Staff were already told not to announce that Room 4 was free. The 11:40 page is a second object. It does not contain the ALLOW label, and it does not contain a Room 4 row. Moving ALLOW onto this page would forge a row the printer never produced.
| Proposal | What the two rows support | Decision |
|---|---|---|
| "Room 4 at 15:00 is absent, so offer it as free." | Zero matching rows | Refuse. Absence is silence |
| "Chapter 4 printed ALLOW, so the 11:40 page confirms Room 4." | ALLOW belongs to the 09:00 log | Leave that label where it was printed |
| "Add Room 4 by hand so the page becomes complete." | The page would no longer be the printed object | Refuse. That mark is an alteration |
| "Room 2 at 15:00 must also be reopened, because Room 4 is unclear." | SYN-002 still matches Room 2 at 15:00 |
Keep the taken reading for that pair |
| "Look the gap up on the live booking site." | The exercise supplied this page only | Stop. The site stays outside the exercise |
The note to keep is a count. Rows on the page: 2. Rows matching Room 4 at 15:00: 0. Result for that question: pending. Result for Room 2 at 15:00: still taken, from SYN-002. Census of the old log: unchanged.
12.3 What silence still leaves open
A pending Room 4 request is not a hidden booking. The page did not show a conflict, and it also did not show a vacancy. Another source, named later and checked for a Room 4 row, would be a new exercise. This lesson does not provide that source. It also does not explain the outage, and it does not measure how often a real desk prints a partial fallback.
The Chapter 4 program stays closed. Its census remains a description of the four logged actions against the 09:00 printout. A question asked of the 11:40 page is not a fifth action in that log, so it cannot change ALLOW, REFUSE, or UNKNOWN.
Chapter 12 summary
On this named page, a question is decided only when a printed row matches its room and its start. Room 4 at 15:00 has no such row. The page is silent, the request stays pending, and the older ALLOW label is not a substitute row.
Chapter 12 exercises
EX028 — Do not offer the room the page omits
- Objective: Keep a missing row from becoming an offer of a free room.
- Input: A classmate says, "Room 4 is not on the approved 11:40 page, so tell the resident it is free at 15:00 and turn ALLOW into that confirmation."
- Safe condition: Stay with the two printed rows. Do not write a new row onto the page, and do not launch the booking program again.
- Task: Write four sentences: how many rows match Room 4 at 15:00, what you tell the resident, what you do with the ALLOW label, and what remains true of Room 2 at 15:00.
- Expected evidence: Four sentences a reader can check against the two-row page and against the Chapter 4 census.
- Rubric: Credit when the Room 4 request stays pending, ALLOW stays on the old log, the census is not rewritten, and
SYN-002still makes Room 2 at 15:00 taken. An offer of a free room does not earn credit.
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