# Relationships Between Architecture Principles

**In short:** Architecture principles support one another. Based on the verified facts: high cohesion tends to bring low coupling, and low coupling signals a well-structured system that avoids rigidity.

## Explanation

Architecture principles are rules of thumb for good design. They do not stand alone. Some support others. This article covers only the links that the verified facts back.

**Cohesion and coupling.** Cohesion describes how well the parts inside one element belong together. Coupling describes how strongly elements depend on each other. The two are linked. Striving for high cohesion often brings low coupling. It also tends to bring reusability and understandability. See *Coupling and Cohesion* and *High Cohesion* for the basics.

**Why low coupling matters.** Low coupling is often a sign of a well-structured system. The iSAQB foundation curriculum lists "loose, but functionally sufficient, coupling" of building blocks as a design principle. The word "sufficient" matters: the coupling must still let the parts do their job.

**Separation of concerns.** This principle says that no element should share the responsibilities of another. It should also not hold unrelated responsibilities. Clear responsibilities keep elements apart. That fits the aim of loose coupling.

**What the principles protect against.** Design principles aim to avoid rigidity. A rigid system is hard to change, because each change affects many other elements. Loose coupling and clear responsibilities limit how far a change spreads.

**Reading the links.** You can picture the principles as a network. One principle supports another, and together they push the design toward the same goals. The verified facts here do not describe the other links in detail. See the related articles for each principle.

## Example

A team builds an online shop. The orders part holds only order logic. The payments part holds only payment logic. Each part has one clear job, so each part is cohesive. The two parts need little knowledge of each other, so coupling stays low. When the team changes how payments work, few other parts are affected.

## Trade-offs

The facts say coupling must be loose but still functionally sufficient. Cutting dependencies too far can leave building blocks unable to do their work. Apply the principles together and check each against the real needs of the system.



## Checks

- The documentation states that coupling between building blocks is loose but still functionally sufficient.
- Each element has clear responsibilities and does not mix in unrelated ones.
- Elements are cohesive, and the document links this to low coupling.

## Related

- [Coupling and Cohesion](https://arc.fuet.ch/concepts/principles/coupling-and-cohesion.md)
- [High Cohesion](https://arc.fuet.ch/concepts/principles/high-cohesion.md)
- [Loose Coupling](https://arc.fuet.ch/concepts/principles/loose-coupling.md)
- [Separation of Concerns](https://arc.fuet.ch/concepts/principles/separation-of-concerns.md)
- [Design for Change](https://arc.fuet.ch/concepts/principles/design-for-change.md)
- [Architecture Principle](https://arc.fuet.ch/concepts/principles/architecture-principle.md)
- [Conflicting Architecture Principles](https://arc.fuet.ch/concepts/principles/conflicting-architecture-principles.md)
- [Working with Principles](https://arc.fuet.ch/concepts/principles/working-with-principles.md)

## Sources

- [iSAQB® Glossary of Software Architecture Terminology](https://public.isaqb.org/glossary/glossary-en.html) — public.isaqb.org, accessed 2026-11-09
- [Curriculum forCertified Professional forSoftware Architecture (CPSA)®: Foundation Level](https://public.isaqb.org/curriculum-foundation/curriculum-foundation-en.html) — public.isaqb.org, accessed 2026-11-09