Residual requirements and architectural residues

Monitoring running systems is a useful technique available to requirements engineers, to ensure that systems meet their requirements and in some cases to ensure that they obey the assumptions under which they were created. This report studies relationships between the original requirements and the monitoring infrastructure. It postulates that the monitored requirements are in fact just compilations of original requirements, called residual requirements. Dynamic architectural models have become important tools for expressing requirements on modem distributed systems. Monitoring residual requirements will be seen to involve architectural residues, skeletal run-time images of the original logical architecture. An example sales support system is used to illustrate the issues involved, employing modest extensions to the Acme architecture description language to reason about architectural dynamism.