“…Rule classes may vary from the more restrictive ones, like edge replacement (Drewes & Kreowski & Habel, 1997) or node replacement (Engelfriet, & Rozenberg, 1997), to the more general ones, like doublepushout rules , single-pushout rules , or PROGRES rules (Schürr, 1997). In this paper, we use rules of the form r = (L → K R) where L and R are graphs (the left-and right-hand side of r, respectively) and K is a set of nodes shared by L and R. In a graphical representation of r, L and R are drawn as usual, with numbers uniquely identifying the nodes in K. Its application means to replace an occurrence of L with R such that the common part K is kept.…”