Backup and staging are separate bits | Rapid course Application and software supply chain security

Lesson map

Lesson 17. Map, example, EX063.

flowchart TD
  B["backup taken = True"] --> P["Its own bracket"]
  S["tested on staging copy = True"] --> R["Its own bracket"]
  P --> Q{"Does one True imply the other?"}
  R --> Q
  Q -->|No| K["Both happen to be true in this file"]

Two keys. Either could have been false alone. In this file, neither is.

Logical drawing

[x] backup taken
[x] tested on staging copy
date stored on either bit: none
donor row stored on either bit: none

Learning outcomes

After this chapter, you should be able to:

Keep the two Booleans independent.
Place the restore and the synthetic donations in prose.
Refuse a date or a donor record inside either bit.

17.1 Each literal answers one question. Neither bit describes the bytes.

backup taken is the literal True. tested on staging copy is another literal True. The dictionary does not check that the second is true only when the first is true. A file could store a test without a backup, or a backup without a test. This file stores both as true. The two brackets are two lines because they are two keys.

The prose says Owen restored a backup to staging once, and later tested donate-form there with synthetic donations. The restore is one event told in sentences. It is not a date inside either Boolean. The synthetic donations are not rows in checks. No donor name, no amount, and no card number is available to copy. Card numbers are described as staying with the payment provider. The provider's systems are out of scope, and this dictionary does not assess them.

A change log line, in the prose, records what changed, when, and how to undo it. Those three log fields are not keys in checks. The bits do not say which backup file was used. Asking the script for a filename asks for a string it does not hold.

Lesson table; scroll horizontally to read all columns →

Key	Value	What the prose adds, outside the bit
backup taken	True	One restore onto staging, earlier
tested on staging copy	True	Synthetic donations, no real donor rows
either bit	no date field	The change log carries "when", in prose

17.2 Worked example

Lesson table; scroll horizontally to read all columns →

Claim	Independence	Decision
Both brackets are `x`	Both literals are `True`	Keep
A backup without a test is representable	The bits do not imply each other	Keep as a property of the dictionary
"The script printed the restore date."	No date is stored	Refuse
"Synthetic donors are rows in `checks`."	They are prose only	Refuse

Synthetic case. Staging uses synthetic records. None are listed in the checklist.

Errors and limits

Do not fill a Boolean with a filename, a date, or a donor.

Apply

EX063 — Two bits. Both backup and staging print x. A classmate treats them as one fact, adds the restore date, and lists a synthetic donor. What does each key store?
Show marking criteria
Rubric: 3 = each key stores its own literal True; one does not imply the other in the program, though both are true here; the date and the donor stay prose;; 2 = two Booleans stay and the date stays out;; 1 = one bit;; 0 = none.