modularitetsindex

Modularitetsindex, or the modularity index, is a metric used in design and systems engineering to quantify how modular a given system is. It reflects the extent to which the system can be divided into relatively independent modules that interact through well-defined interfaces, enabling independent development, testing, replacement and evolution.

In practice, the index is calculated from a representation of the system as a set of modules and the dependencies among them. A common approach is to model modules as nodes in a graph and dependencies as edges. A simple version of the modularitetsindex is the ratio of internal dependencies (those that stay within the same module) to the total number of dependencies (internal plus external). Values close to 1 indicate high modularity, while values near 0 indicate strong cross-module coupling. Some approaches also weight dependencies by interface complexity or frequency of communication, or use network-based metrics to capture community structure among modules.

The modularitetsindex is used to assess current architecture, compare design options, and guide refactoring. It is applied in software engineering to evaluate architecture, in product design to organize components, in manufacturing and supply chains to structure modules, and in urban planning or organizational design to study functional decomposition. Because module boundaries affect maintainability, adaptability, and reusability, the index is often tracked over time or across scenarios to support decision making.

Limitations include dependence on how modules are defined, the granularity of decomposition, and the ignoring of non-structural factors such as quality of interfaces or runtime behavior. Therefore the index should be used alongside qualitative assessments and other metrics.