In this section, we introduce semi-MSL that finds a
unified low-dimensional and sufficiently smooth subspace
over all views simultaneously. To clearly explain the
technique details of the proposed semi-MSL, we present
important notations used in the rest of this paper. Capital
letters, e.g., X, represent the cartoon database. Lower case
letters, e.g., x, represent cartoon characters, and xi is the
ith cartoon character of X. Superscript (i), e.g., X(i) and x(i)
, represents the cartoon character’s feature from the ith
view. Based on these notations, semi-MSL can be
described under the umbrella of the PAF [2].