Graph-based models with simulated nodes

An overlay system, comprising:

• a storage element configured to store an executable graph-based model;
• and
• processing circuitry that is coupled to the storage element, and configured to:
• receive a first stimulus associated with simulation of a first object of an external system in the executable graph-based model;
• instantiate, in the executable graph-based model, a first preliminary node for the first object, wherein the first preliminary node interfaces the first object in the executable graph-based model, and wherein the first preliminary node is associated with a first set of attributes;
• map, to the first set of attributes, a first set of attribute values associated with the first object;
• instantiate, in association with the first preliminary node, a first simulation overlay node in the executable graph-based model;
• customize the first preliminary node based on the association with the first simulation overlay node;
• and
• generate, based on the customization of the first preliminary node, a first simulated node simulating the first object in the executable graph-based model.