Five ontological levels to describe and evaluate software architectures

Quality models for software architecture are taxonomies of quality attributes, commonly used to specify and evaluate nonfunctionalrequirements. Most quality models offer a two-level approach, distinguishing externally observable and internallymeasurable attributes, yielding stakeholder-specific composite quality criteria. Much effort is devoted to determine whichinternal attributes influence which external ones, and most models stick to a two-level hierarchy. This paper argues that thisapparent dual order obscures the fact that requirements are made by different stakeholder about different subjects, and theword “architecture” means different things to each of them: the organization of a system, a description of such organization,and the process of elaborating such descriptions. The proposed scheme organizes architecture attributes according to fiveontological (descriptive) levels, each of them with different concerns, types of users and available measurement techniques:computations, deployables (binaries/configurations), software (texts), specifications (of architecture and/or design), andarchitecture process. Finally, levels and stakeholders are related to specific architecture views.