IVP Core Theory
This is the formal heart of the Independent Variation Principle as applied to software. Here we explain the model the theory works on, the principle itself, and what follows from it.
The principle is stated and proved in the published paper on the Independent Variation Principle [1].
The core theory has seven parts.
- The software system tuple. The model of a software system the principle is stated over: purpose, domain knowledge, elements, coupling, change drivers, and the change-driver assignment.
- Change drivers and assignment. What a change driver is, how elements are assigned to them, and how the assignment is discovered from the domain.
- The structural formulation of IVP. The statement of the principle itself — the one-sentence Γ-equivalence rule and the four conditions.
- The Γ-equivalence partition. The object the principle produces, and what purity and completeness mean.
- The partition theorem. The result that the compliant module structure is uniquely the Γ-equivalence partition.
- Scope and validity conditions. The premises, preconditions, and applicability gates the results depend on.
- Consequences and application. What the theory implies for structuring software and the six-step procedure for applying it.
The knowledge-embodiment theorem — which links maximal cohesion to the embodiment of domain knowledge — is a result of the cohesion theory, not of IVP itself. It is treated on the cohesion page, because it states a property of cohesion, and cohesion is a design principle distinct from IVP.
The formal development. The definitions, theorems, and proofs behind this page are published in:
- The Independent Variation Principle — Zenodo, 2026 — doi:10.5281/zenodo.20794332
References
[1]
Y. Loth, “The independent variation principle.” Zenodo, Jun. 2026. doi: 10.5281/zenodo.20794332.