This paper describes the application of requirements engineering concepts to
support the analysis of the impact of new software systems on system-wide goals.
Requirements on a new or revised software component of a socio-technical system not
only have implications on the goals of the subsystem itself, but they also impact upon
the goals of the existing integrated system. In industries such as air traffic
management and healthcare, impacts need to be identified and demonstrated in order
to assess concerns such as risk, safety, and accuracy.
A method called PiLGRIM was developed which integrates means-end
relationships within goal modelling with knowledge associated with the application
domain. The relationship between domain knowledge and requirements, as described
in a satisfaction argument, adds traceability rationale to help determine the impacts
of new requirements across a network of heterogeneous actors. We report procedures
that human analysts follow to use the concepts of satisfaction arguments in a software
tool for i* goal modelling. Results were demonstrated using models and arguments
developed in two case studies, each featuring a distinct socio-technical system – a
new controlled airspace infringement detection tool for NATS (the UKs air
navigation service provider), and a new version of the UKs HIV/AIDS patient
reporting system. Results provided evidence towards our claims that the conceptual
integration of i* and satisfaction arguments is usable and useful to human analysts,
and that the PiLGRIM impact analysis procedures and tool support are effective and
scalable to model and analyse large and complex socio-technical systems. 