EII emphasizes neither on correctness nor tractability, but speed and simplicity. Another challenge that has been posed is predictive coding's computational tractability. Mainstream economics uses infinitesimal values in much of its analysis for reasons of mathematical tractability. Tractability can be obtained by considering specific classes of constraint satisfaction problems. In order to retain model tractability, one may require parameters to be piecewise-constant. A frequency shift does not undermine the mathematical tractability of the complex signal representation. Herding instincts and tractability can be assessed in noncompetitive herding tests. A sufficient condition for tractability is related to expressibility in Datalog. Tractability can be obtained by restricting the possible domains or constraints. Though wolves are trainable, they lack the same degree of tractability seen in dogs. Although this assumption makes the analysis less robust, it increases tractability. Due to its relevance and tractability it is a common setting in the literature. These systems are used because of their genetic tractability and their fast growth. This technique later proved very useful in showing fixed-parameter tractability results. In this formulation, it is easy to check if any of the tractability conditions hold.