"Isolated" is the opposite of "situated". Isolated nodes have no situation features, which means that no values can be "conferred" upon their SIDPs. This is the reason why i-nodes are not well-formed unless they exhibit a built-in value for at least one of their SIDPs; in the absence of such a built-in value, there would be no indication of the subject for which an i-node is a proxy.

See comments to parid2178.