  In branching simulation, a novel approach to simulation presented in this
paper, a multiplicity of plausible scenarios are concurrently developed and
implemented. In conventional simulations of complex systems, there arise from
time to time uncertainties as to which of two or more alternatives are more
likely to be pursued by the system being simulated. Under these conditions the
simulationist makes a judicious choice of one of these alternatives and embeds
this choice in the simulation model. By contrast, in the branching approach,
two or more of such alternatives (or branches) are included in the model and
implemented for concurrent computer solution. The theoretical foundations for
branching simulation as a computational process are in the domains of
alternating Turing machines, molecular computing, and E-machines. Branching
simulations constitute the development of diagrams of scenarios representing
significant, alternative flows of events. Logical means for interpretation and
investigation of the branching simulation and prediction are provided by the
logical theories of possible worlds, which have been formalized by the
construction of logical varieties. Under certain conditions, the branching
approach can considerably enhance the efficiency of computer simulations and
provide more complete insights into the interpretation of predictions based on
simulations. As an example, the concepts developed in this paper have been
applied to a simulation task that plays an important role in radiology - the
noninvasive treatment of brain aneurysms.
