A decision support model for choosing an application server architecture at the design stage of CASE tools

Selecting an application server architecture at the software system design stage involves accounting for a wide range of heterogeneous factors, including expected workload, scalability requirements, collaborative usage modes, budget constraints, and the development team’s qualifications. Architectural solutions are classified according to two independent dimensions: the number of tiers (two-tier, three-tier, n-tier) and the organization of application logic (monolithic, modular, microservice-based), which results in a variety of possible configuration options. However, the lack of formalized methodologies complicates the substantiated selection of an optimal combination. The proposed decision support model is based on the Analytic Hierarchy Process (AHP) by Saaty and incorporates a six-stage algorithm: formation of a set of criteria, determination of their weights through pairwise comparisons, construction of a set of admissible alternatives, evaluation of alternatives with respect to each criterion, computation of global priorities, and analysis of transitions between architectures. The application of the model is demonstrated using CASE tools—a class of software products for which collaborative model editing and remote access via a web interface are of primary importance. The practical case considers the transition of a desktop CASE tool with a two-tier monolithic architecture to another environment; the calculation of global priorities shows that the “three-tier + modular” configuration achieves the highest score compared to other alternatives. The introduction of a threshold value for priority differences enables a formal justification of the transition decision and the determination of an optimal sequence of intermediate migration stages. The results can be used by software architects when designing new systems and planning the modernization of existing ones.