In order to speak of something as a system, we must be able to state clearly: (1) the holistic behaviour which we are focusing on; (2) the parts within the thing, and the interactions among these parts, which cause the holistic behaviour we have defined; (3) the way in which this interaction, among these parts, causes the holistic behaviour defined. If we can do these three, it means we have an abstract working model of the holistic behaviour in the thing. In this case, we may properly call the thing a system, If we cannot do these three, we have no model, and it is meaningless to call the thing a system.

virtual-dom exposes a set of objects designed for representing DOM nodes. A "Document Object Model Model" might seem like a strange term, but it is exactly that. It's a native JavaScript tree structure that represents a native DOM node tree.