We note that discoveries of deficiencies in the original rules have been made before in the context of developing computer-based implementations. This was certainly the case in 1993, when subrules 4a, 4b, and 4c were proposed by a group developing a stereochemical module for the LHASA computer-aided synthesis analysis program. Not surprisingly, predating the open-source collaborative environment and not having a concise reference in hand, machine implementations of the CIP Rules to date have been only marginally successful. Certainly, many software developers have implemented the CIP Rules to one extent or another, but recent analysis of available software packages clearly demonstrates that there is much disagreement among these implementations, even for relatively simple compounds, among several highly respected software packages. In the spring of 2017, concurrent discussions started in two forums, the IUPAC Blue Book Project, focused on preparation of errata for BB 2013, and the Blue Obelisk Group, focused on implementation issues of CIP rules in algorithmic form. The result of these lively discussions has been a reason for coordinated and thorough analysis of the CIP Rules, with the aim of concurrent development and improvement of four software packages: Jmol , Centres , ChemSketch , and Balloon . Our joint efforts ensured that multiple, validated, independent machine implementations of the CIP Rules are made available to the cheminformatics community, as well as to anyone interested in stereochemistry and chemical nomenclature. In fact, the results of our work have already been incorporated into an interactive web site utilizing JSmol. As we sought consensus when there were issues and questions as to interpretation of the rules or correctness of BB 2013 examples, we turned to the use of finite acyclic digraphs, the assumption being that analysis of digraphs should always be the final arbiter in any dispute relating to stereochemistry. The use of digraphs in our discussions allowed for one of three possible conclusions: (a) that the disagreement was due to different interpretations of CIP rules among software developers, (b) that there was a problem with an algorithm or its implementation in code, or (c) that the CIP rules themselves were flawed. In fact, all three of these possibilities were encountered in the process of coming to consensus, including the discovery of a small number of errors in the Blue Book, two minor flaws in the CIP rules, and a proposal for a new rule.