The article says that is a contraction for , i.e., is a function of two arguments. So apparently is the derivative with respect to the second argument.
"[...] These variables give a measure of correspondence between signal and model relative to all other models, . A mechanism of concept formation and learning, an internal dynamics of the modeling fields (MF) is defined as follows,
Parameter determines the iteration step and speed of convergence of the MF system; can be interpreted as a number of signals associated with or coming from a concept object . As already mentioned, in the MF internal dynamics, similarity measures are adapted so that their fuzziness is matched to the model uncertainty. [...]"
http://www.leonid-perlovsky.com/4%20-%20Mehler.pdf (page 368)
What does it mean to take a partial derivative with respect to a model i.e. ?
Thanks in advance,