COMPUTER METHOD FOR EXECUTING TRANSFORMATION RULES

A computer method is disclosed for using rewrite rules of the form X(Y)Z=(R) where X is the left context, Y is the body of the rule, Z is the right context and R is the replacement value for Y if the rule is successful. The method places restrictions on how the rules are defined to make it possible to organize the rules so that they can be indexed efficiently. In particular, the body of the rules is not allowed to be defined in generic terms, whereas this restriction is not applied to the left and right context of the rules. The rules are scanned so that the first rule that matches the body and its context is the one that applies. Ordering the rules into a hierarchy makes it possible to have exceptions to any particular rule. The method encompasses a model where the rules are applied to any input string. When no rules apply to any character of the input string, a default rule to copy the string is applied. This guarantees that the process will always terminate and that it will be loop-free.