Section 10 of 103
9. Shall, Shall Not, Should, May and Can
Stable section ID: S05-CON-015-SECTION-10 · 10 content blocks
The following modal verbs shall have controlled meanings throughout System05:
- Shall establishes a mandatory requirement.
- Shall not establishes a mandatory prohibition.
- Should establishes a recommendation for which justified alternatives may exist.
- Should not establishes a recommendation against a particular action or condition.
- May establishes permission or an allowable option.
- Can describes capability, possibility, or a factual condition and does not grant permission.
A statement using “shall” shall identify an obligation capable of implementation, assessment, or governance. Multiple independent obligations should not be combined into one requirement where separate verification is necessary.
The word “must” should be avoided as a System05 normative keyword except when accurately reproducing an external legal or regulatory obligation. “Will” describes an expected future condition or declared intention and shall not be used as a substitute for “shall.”
Permission expressed by “may” does not remove any applicable safety, legal, compatibility, or verification obligation.