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the hamiltonian spanning graph problem (Saul Griffith) solution to the hamiltonian spanning graph problem  subdivision of units (Saul Griffith), with algorithm for building spanning graphs additively (global solution through local problem solving :) Saul's enumeration of states for 2d figure filling by vertex connected squares 
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This is the system previously proposed, with two tile types (one with 3N&1S faces, and one with 3S&1N faces)... I propose a modified system with only one tile type, in terms of edge condition arrangment (two of each condition, per tile). This satisfies all of the strong bonding and turning characteristics of the previous system. Furthermore, one side of a string provides enough information for replication(!). More on replication to come... Considering rotations of the connection scheme (diagonal vertices), the full set of primitives, for a one dimensional system that can fill any continuous two dimensional figure... 