|
Right-sorted BPs have the keyword "gap" on the OEBP.
A Bongard Problem with a gap showcases two completely separate classes of objects.
For example, the Bongard Problem "white vs. black" (BP962) has a gap; there is no obvious choice of shared context between the two sides. One could imagine there is a spectrum of grays between them, or that there is a space of partially filled black-and-white images between them, or any number of other ambient contexts.
Bongard Problems about comparing quantities on a spectrum should not usually be considered "gap" BPs. (Discrete spectra perhaps.) A spectrum establishes a shared context, with examples on both sides of the BP landing somewhere on it. (However, if it is reasonable to imagine getting the solution without noticing a spectrum in between, it could be a gap, since the ambient context is unclear.)
Bongard Problems with gaps may seem particularly arbitrary when the two classes of objects are particularly unrelated. | 
