The familiar solar-system/atom analogy has been used in a number of contexts to illustrate the analogical mapping process (e.g., Gentner, 1983; Keane, Ledgeway, & Duff, 1994). In this analogy, the sun and planet in the solar-system domain are analogous to the nucleus and planet in the atom domain. The higher-order structure of the two analogs helps constrain the possible mappings formed.
The solar-system/atom model simulates the mapping process between these two domains. The model maps planet and sun in the solar-system domain to the electron and nucleus, respectively, in the atom domain. The running model displays the trace of this mapping process, as shown in Table 2 in the paper. Note that the trace need not exactly conform to that in Table 2 due to the fact that the model may select different analog components to map or may commit retrieval errors in the process.