Software Design Modularity Assessment in Legacy Systems

Abstract

Software design modularity assessment is an important practice in legacy systems where long-term maintenance, repeated enhancements, and technology changes can gradually weaken the original software structure. In enterprise applications, poor modularity may lead to tight coupling, duplicated logic, unclear module boundaries, difficult testing, slow defect correction, and high maintenance cost. This article discusses how modularity assessment helps teams evaluate the structural quality of legacy software and identify areas that require refactoring or redesign. It explains the role of module dependency analysis, cohesion measurement, coupling analysis, interface review, change impact tracking, and code structure inspection in understanding modular weaknesses. The article also highlights common challenges such as outdated documentation, hidden dependencies, obsolete technologies, mixed business logic, and limited knowledge of original design decisions. A structured modularity assessment approach is presented to improve maintainability, reduce rework, support modernization planning, and extend the useful life of legacy systems. The study concludes that effective design modularity assessment strengthens software maintainability, improves change control, and supports sustainable evolution of enterprise applications.