Transformation rules use the same syntax as edge-addition rules to specify preconditions, and have an additional transformational part. This transformational part consists of node deletions, node additions, edge deletions and edge additions, also to the newly created nodes.
![\begin{verbsyntax}\synrule{XGRSRule}{[ Options ] [ FIRSTCode ] RuleTest '==>' }
...
...Deleted ] [ NodesToBeAdded ] ',' ] Predicates [ LASTCode ] ';'}
\end{verbsyntax}](img67.gif)
Rule groups options, rule options, FIRST- and LAST-Code behave in the same way as with EARS rules.
Note that currently the user himself has to guarantee the termination of a XGRS. There is no automatic check for that, neither a test for confluence. See also the article on XGRS [Aßm96a], whose method is currently not implemented..