However, as exploited in [10], for these to satisfy the axioms of a D-metric it is not
necessary that d satisfy the triangle inequality, only that it be a semi-metric.
In a subsequent series of papers Dhage attempted to develop topological structures
in such spaces. He claimed that D-metrics provide a generalization of ordinary
metric functions and went on to present several fixed point results. Subsequently,
these works have been the basis for over 40 papers by Dhage and other authors.