The choice of which package to use depends on the nature of the system BP wants to investigate. Powersim and ithink come from companies set up in the mid-1980s. Powersim is now based at Isdalsto in Norway and started off as SimSim. The company behind ithink is the US-based High Performance Systems of Hanover, New Hampshire. A project in SD starts with a computer model of the business problem under investigation.
Models exist for all manner of system, in the business world and outside.
While BP has focused on big engineering projects, with excursions into other areas, other companies have used models more extensively for business processes. Unlike some packages, ithink and Powersim produce what are known as high level models. These capture just enough detail to describe a system. Fast, for example, contains minimal engineering details. Even without complex details of a system, it can take time to create a robust model that will deliver meaningful results.