Multiply bonded atoms are considered as if they were the equivalent of singly bonded ones, and the descriptors ?
External formats which utilize this convention include SMILES and Sybil Line Notation. One limitation of this convention is constitutional incompleteness, for which Custer has proposed a compatible extension, and occurs when a loss of information is incurred by mapping the original molecule's graph onto a hierarchical diagraph. A second limitation is referred to as the reconstruction problem, and for homo-substituted cycloalkanes the resulting ambiguities generally increases with ring sizes greater than 7.  Multiply bonded atoms are considered as if they were the equivalent of singly bonded ones, and the descriptors ?R and S indicate in what direction the lowest ordered substituent is pointing. Having the benefit of being independent of both the magnitude and the sign of rotation, for 10 points, identify this triply eponymous set of rules used for specifying the sense of chirality at tetrahedral stereogenic centers.   
External formats which utilize this convention include SMILES and Sybil Line Notation.
{Cahn}-{Ingold}-{Prelog} Priority Rules