Abstract: A method, apparatus, article of manufacture, and a memory structure for generating a sequence of character strings is disclosed. This is accomplished by making multiple consecutive variations of a single character-string pattern where each variation differs from the previous one in a systematic way. The pattern is not restricted in form or in content, and the variations can include adding, deleting, and modifying lines and strings in the pattern, and making no change. This is implemented by executing production rules on a template. In one embodiment, the method herein described begins by defining a template comprising a plurality of template character strings, and defining an ordered series of production rules, each with a comparison field, an operator, and a substitution field comprising a list of elements defining an initial value and a current value. The current value of each production rule is set to the initial value, and the production rules are applied to the template one at a time in execution order.