## Chapter 6 — anyone-with-link is not the token public ### Lesson map Lesson 06. Map, example, EX052. ```mermaid flowchart TD S["A setting string"] --> M{"Is it a member of allowed for that Boolean?"} M -->|Yes| K["The triple stays out of bad"] M -->|No| B["The triple is printed"] ``` Membership is exact. It is not a rank. ### Logical drawing ```text allowed when sensitive: staff, admins allowed when not sensitive: staff, admins, public present failure token: anyone-with-link absent from this list: a sensitive triple whose setting is public ``` ### Learning outcomes After this chapter, you should be able to: 1. Explain the failure test as set membership. 2. Separate the string `public` from the string `anyone-with-link`. 3. Refuse a claim that every failure in this run had to be sensitive. ### 6.1 The predicate does not rank the strings. The comprehension asks one question: is this setting one of the strings in the set selected by the Boolean? It does not ask which string is narrower. `staff` and `admins` are both members of the sensitive set, so a sensitive triple using either string passes. The program never orders those two members. `public` is a member only of the non-sensitive set. A sensitive triple whose setting was the string `public` would fail, because that string is absent from `allowed[True]`. No triple in the eight has that combination. The three failures all carry `anyone-with-link`, which is absent from both sets. A non-sensitive triple with `anyone-with-link` would also fail. This file contains no such triple, so the failure list and the sensitive-failure list happen to name the same three objects. That coincidence is a property of these eight rows. It is not a definition of the predicate. `price-list.pdf` and `logo.png` pass only because their setting is the string `public`, not because a link was inspected. The link text itself is absent from the triple. The setting name is what the filter reads. Constructing or guessing an address is outside this chapter and outside the clinic's authority. ### 6.2 Worked example | Claim about a triple | Membership fact | Decision | |---|---|---| | `logo.png` at `public` passes | Non-sensitive, and `public` is allowed | Keep | | `booking-app-config` at `admins` passes | Sensitive, and `admins` is allowed | Keep | | A sensitive `public` row would pass | `public` is not in `allowed[True]` | Refuse | | "Too wide means sensitive" | True only of this particular failure list | Refuse | > **Synthetic case.** No link string is stored beside the setting name. ### Errors and limits Do not promote the coincidence of three sensitive failures into the meaning of the test. ### Apply - **EX052 — Two strings.** A classmate says `anyone-with-link` is just the lab's way of writing `public`, and that a sensitive item marked `public` would have passed. What does the set test do, and which failure token is actually present? *Rubric:* 3 = the strings differ; `public` is allowed only when the flag is false; a sensitive `public` triple would fail and none exists; the three failures are `anyone-with-link`; do not print a link;; 2 = the tokens differ and the three failures stay;; 1 = one token;; 0 = none. ### Continue studying — lesson 06 (chapter 06 of 20) [← Chapter 05](#ch-05) · [Course chapter index](../SUBJECTS.md) · [Chapter 07 →](#ch-07) Continue to the next authored lesson. ## Worked answers **EX052.** `anyone-with-link` and `public` are different strings. `public` is allowed only when the sensitive flag is false. A sensitive triple set to `public` would fail, and no such triple exists. The three failures are `anyone-with-link`. No link text is printed.