In the classical approach to digital topology (see e.g. [12] and [13]), graph theoretic tools are used for structuring Z, namely the well-known binary relations of 4-adjacency and 8-adjacency. But neither 4adjacency nor 8-adjacency itself allows an analogue of the Jordan curve theorem (cf. [9]) and, therefore, one has to use a combination of the two adjacencies. To overcome this disadvantage, a...
