Patent ID: 7657422

Claim:
A computer implemented method for generating a Directed Acyclic Graph (DAG) from an initial multi-chain subject to a constraint, the method comprising: expressing the initial multi-chain as a character string that serves as a current input string, wherein the input string expressing the initial multi-chain violates the constraint, and wherein the constraint with respect to a given input string expresses a condition that the given string either satisfies or violates; providing at least one regular expression that expresses the constraint, said at least one regular expression being in a character string format and being denoted as P; applying P to the current input string to generate at least one output string, wherein each generated output string violates the constraint to a lesser extent than does the input string or does not violate the constraint, and wherein each generated output string violating the constraint will serve as a current input string to which the constraint is subsequently applied; if the at least one output string violates the constraint as a result of said applying P then responsive to the at least one output string violating the constraint, recursively repeating said applying P to each current input string that had been determined from applying P previously, until said applying P does not generate any more output strings violating the constraint, wherein a set of the generated output strings that do not violate the constraint represents the DAG; and displaying, on a display device, the set of the generated output strings that do not violate the constraint, wherein said recursively repeating said applying P is performed at least once.