Parameter	Description
$X$	Complete tile set of all samples,$X=\left\{x_1,x_2,\dots ,x_n\right\}$
$x_i$	Single tile,$x_i\in X$
$X_i$	Subset of $X$ corresponding to the $i$th sample,$X_i\subset X$
$F$	Complete VAE-learned feature set,$F=\left\{f_1,f_2,\dots ,f_m\right\}$
$f_i$	Single feature,$f_i\in F$
$A$	Random variable defined over $F$
$T$	Random variable defined over $X$