Boundary spanners-in-practice are individuals who inhabit more than one social world and bring overlapping place perspectives to bear on the function(s) performed within and across each world. Different from nominated boundary spanners, they are practitioners responsible for the 'translation' of each small world's perspectives thereby increasing collaboration effectiveness to permit the small worlds to work synergistically. The literature on Knowledge Management (KM) has emphasized the organizational importance of individuals performing boundary spanning roles by resolving cross-cultural and cross-organizational knowledge system conflicts helping teams pursue common goals through creation of "joint fields" - a third dimension that is co-jointly developed between the two fields or dimensions that the boundary spanner works to bridge. The Copeland and O'Connor Nondeterministic Model of Engineering Design Activity was utilized as the foundation to develop models of communication mechanics and dynamics when multiple simultaneous interactions of the single nondeterministic user model, the BSIP and two Subject Matter Experts (SMEs), engage during design activity in the Problem-Solving Space. The Problem-Solving Space defines the path through the volumes of plausible answers or 'solution spaces' that will satisfice the problem presented to the BSIP and SMEs. Further model refinement was performed to represent expertise seeking behaviors and the physical and mental models constructed by boundary spanners-in-practice during knowledge domain mapping. This was performed by mapping the three levels of communication complexity (transfer, translation and transformation) to each knowledge boundary (syntactic, semantic and pragmatic) that must be bridged during knowledge domain mapping.