Layerlevel

Layerlevel is a conceptual metric used in layered system design to indicate how many layers separate a given component from the system's core services. It is typically represented as a nonnegative integer, where lower numbers denote closer proximity to foundational services and higher numbers indicate higher-level abstractions. In practice, layerlevel is derived from the system’s dependency structure: a component’s layerlevel is usually defined as the maximum layerlevel of its immediate dependencies plus one, with foundational services assigned layerlevel zero.

The concept supports the layering principle, which encourages organizing software into horizontal layers such as presentation, application logic, domain model, and data access. By tracking layerlevel, architects can enforce rules such as no upward dependencies (a higher-level component should not depend on a lower-level one) and stable interface boundaries.

Applications include architectural planning, governance, and refactoring. Layerlevel can guide module packaging, naming, and test strategies, helping teams predict the impact of changes and identify architectural smells, such as large jumps in layerlevel or uneven dependency graphs.

Limitations exist: layerlevel is a simplification of real systems and may not capture dynamic or cross-cutting concerns like plugins, adapters, or runtime wiring. It should be used in combination with other metrics such as cohesion, coupling, and interface stability.

See also: layered architecture, dependency inversion principle, modular design, coupling and cohesion.