src/HOL/IMP/Procs.thy

 type_synonym pname = string
 
 datatype
   com = SKIP 
       | Assign vname aexp        ("_ ::= _" [1000, 61] 61)
-      | Semi   com  com          ("_;/ _"  [60, 61] 60)
+      | Seq    com  com          ("_;/ _"  [60, 61] 60)
       | If     bexp com com     ("(IF _/ THEN _/ ELSE _)"  [0, 0, 61] 61)
       | While  bexp com         ("(WHILE _/ DO _)"  [0, 61] 61)
       | Var    vname com        ("(1{VAR _;;/ _})")
       | Proc   pname com com    ("(1{PROC _ = _;;/ _})")
       | CALL   pname