Process & product improvements / Requirements quality
Invariant Rules Framework for Transfer Systems
A two-layer model for making foundational rules explicit before stories and teams build contradictory behavior around them.
Portfolio-safe reconstruction with fictional banking examples. These are candidate rules for illustration, not statements of any institution’s actual policies or system behavior.
Problem
Teams can write locally correct stories while disagreeing on rules that should hold across the transfer lifecycle. The conflict appears late as rework, unclear tests, or inconsistent outcomes.
What I Designed
A qualification test for always-true, cross-flow constraints; a separate layer for conditional behaviors; and a readiness check that surfaces missing or contradictory rules before build.
Artifact
A simplified rule register showing the distinction between a candidate invariant, a scenario rule, and an unresolved question.
Why It Matters
It creates a shared foundation for decomposition and QA while leaving scenario detail to stories and acceptance criteria.
Artifact / Two-layer rule model
Separate system laws from feature logic
Invariant: a constraint that must hold across relevant states and flows regardless of interface or implementation. Behavioral rule: what happens when a particular condition or action occurs. Test a proposed invariant for universality, cross-flow relevance, business consequence, and unambiguous wording before promoting it.
| Type | Fictional example | How it is used |
|---|---|---|
| Candidate invariant | An instruction cannot be executed without satisfying the approval requirement applicable to its current details. | Validate across create, edit, approval, and execution paths. Confirm with policy owners before treating it as a real rule. |
| Behavioral rule | If a user changes a submitted instruction’s destination, the system asks for review of the revised details. | Define the trigger, permitted state, response, and exceptions in a specific story. |
| Open question | Which changes require a fresh approval decision? | Assign an owner and resolve before stories assume an answer. |
Readiness check
An unclear invariant calls for discovery or a focused decision before a build story relies on it; it does not require freezing the entire product design.