We consider the decision problem for sets of sentences of first-order logic when instead of interpreting function symbols as total functions over the universe of a model (henceforth referred to as the usual interpretation) we interpret them as partial functions. We consider only standard classes, which are certain sets of prenex sentences specified by restrictions on the prefix and on the numbers of k-place predicate and function symbols for each k > 1. Standard classes are introduced in [1â€¦Â CONTINUE READING