Optimal disassembly sequences can be obtained on the basis of linear and mixed-integer programming methods. These are applied to models that are based on disassembly graphs. These graphs represent the possible subassemblies and the transitions (actions) between them. They represent the structure of the assembly in a more abstract manner than assembly drawings do. The translation from assembly drawings into graphs presupposes the selection of the feasible subassemblies and actions. In this contribution a method is discussed that supports the automatic determination of all possible subassemblies, starting from the assembly structure such as represented by drawings etc. It uses the connection diagram and a set of Boolean expressions that represent precedence relations. These are based on part removal in stead of on the disconnection of liaisons. Consequently, actions are transitions between subassemblies. Based on this method, feasible subassemblies and actions can be selected automatically. These represent the full set of data for the establishment of a disassembly graph. The method is demonstrated by the discussion of a number of assemblies that are taken from the literature. It appears that automatic selection of subassemblies is possible. Based on this selection, the set of actions can be defined and the disassembly graph can be established automatically.