The organization of this paper is as follows. In Sec. II we describe the data structure, mapping functions, and operations on SMARTS that are required for automated search. In Sec. III we describe the deterministic searching scheme and how automated chemical perception is performed. In Sec. IV we then show how SMARTS are formed into a hierarchy to provide a chemical perception model. In the Methods (Sec. V) we describe how the SMARTS clusterings are performed. In the Results (Sec. VI) we assess the performance and accuracy of the resulting SMARTS hierarchies on the three experiments described above, and show that the BESMARTS method described in this work is sufficient to build custom chemical perception models for force field design.