Requirements, architecture, and quality in a mission critical system: 12 lessons learned

Abstract

Public tender processes typically start with a comprehensive specification phase, where representatives of the eventual owner of the system, usually together with a hired group of consultants, spend a considerable amount of time to determine the needs of the owner. For the company that implements the system, this setup introduces two major challenges: (1) the written down requirements can never truly describe to a person, at least to one external to the specification process, the true intent behind the requirement; (2) the vision of the future system, stemming from the original idea, will change during the specification process – over time simultaneously invalidating at least some of the requirements. This paper reflects the experiences encountered in a large-scale mission critical information system – ERICA, an information system for the emergency services in Finland – regarding design, implementation, and deployment. Based on the experiences we propose more dynamic ways of system specification, leading to simpler design, implementation, and deployment phases and finally to a better perceived quality.