A space in which it holds is called Ptolemaic. For instance, consider the four-vertex cycle graph, shown in the figure, with all edge lengths equal to 1. The sum of the products of opposite sides is 2.
The term "Ptolemaic" refers to a space that contains something.  For example, take a look at the four-vertex cycle graph depicted in the figure, where each edge has a length of one. The product of the lengths of opposite sides equals two.