boundarystate

Boundarystate is a term used in systems theory and computer modeling to denote the state of a system at its interface with other systems or subsystems. It captures boundary conditions, external inputs, and constraints that influence how the internal state evolves when components interact. The concept supports modular design by making interface behavior explicit separate from internal dynamics.

Although not widely standardized, boundarystate is described in various niche literatures as a state embedded at the boundary between modules. In this sense it can be seen as a memory of past interactions, an envelope of permitted exchanges, and a carrier of timing and sequencing information that governs the next transition.

In practice, a boundarystate may include variables for external messages, timing constraints, and allowed actions, and it may be deterministic or probabilistic. It is used in discrete-event simulations, component-based design, and formal methods to reason about interface properties, such as compatibility, safety, and liveness, without requiring full access to the internal state of the partner module.

Applications span software architecture, cyber-physical systems, protocol design, and model checking, where clearly defined boundary behavior helps verify correct composition of systems. The term is closely related to the notion of boundary conditions in mathematics and to interface contracts in software engineering.

See also: boundary condition, state machine, interface contract, modular design, component-based modeling.