An approach to solving systemic problems of a digital twin in a single information space is considered, taking into account the presence of uncertainty. The solution of the system tasks of the digital twin is implemented on the basis of system-information models using the Unified System Information Space (USIS) and Product Lifecycle System Information (PLSI) software products, which are a platform for product lifecycle management and are system-compatible with Product Lifecycle Management (PLM). One of the solutions to information system problems is to estimate the value of the system uncertainty based on the system-information model of the dynamic processes of the digital twin in the system (USIS + PLSI + PLM), which characterize the stability of the system and optimize its state. A mathematical model of information interaction between the elements of the system is proposed, which is formalized on the basis of the methodology of the system-information approach. The presented approach to the description of the system-information process and system is a theoretical platform for solving system problems of analysis, synthesis, identification, observability, forecasting, estimation, solvability, control, stability, optimization, and dynamics based on system-information models of processes and systems system-based digital twin (USIS + PLSI + PLM).