The class of decision problems of the form (x,k) (k a parameter) that are solvable in space O(f(k) log(n)) and time O(f(k) nc), by a nondeterministic Turing machine, for some function f. The algorithm used may depend on k.
Contained in XNL, which has the same space restriction but allows runtimes of O(nf(k)).
Without the nondeterminism, this would also be contained in FPT, as the runtime is fixed-parameter tractable. But, it is nondeterministic.
Reference: [2]
No class.