Rules in a rule group are specified either in the style of (if they are edge-addition rules), or in the style of graph rewrite rules. Each rule consists of a rule test part and a rule transformation part. Edge-addition rules only allow predicates in their transformation part. Each rule may be accompanied by rule options, FIRST- and LAST-code. Rules are either enclosed in '(' ')' brackets or they end with a ';'. Facts are explained in section 3.8.1, transformation rules in section 3.7.
