import edu.neu.ccs.demeter.dj.*;
import java.util.*; 

Exps = 
  <exps> CommaList(Exp) 
  [*l "equations" <eqs> CommaList(Equation)].
Exp : Simple | Compound | QuantifierCompound.
Simple : SourceEdgeStepsTarget | Sequential.
SourceEdgeStepsTarget : Forward | Backward | 
	 Later | UpOverDown common
  <source> ClassName 
  ["edge" EdgeName] [<steps> Steps] 
  <target> ClassName.
Forward = "->".
Backward = "<-".
Later = "->X<-".
UpOverDown = "=>X<=".
Sequential = "seq" <source> ClassName CommaList(ClassName).
Exists = "exists" CommaList(ClassName) *l Exp.

Steps: Unlimited | Limited.
// if steps is absent, the default meaning is unlimited
Unlimited = "*".
Limited = <i> Integer.

Compound = Op <args> CommaList(Exp).
Op : Join | Union.
Join = "join".
Union = "union".

QuantifierCompound : Exists.

Equation = *l <left> Exp "=" *l <right> Exp.
ClassName = Ident.
EdgeName = Ident.

CommaList(S) ~ "(" *l + S {"," *l S *s} - *l ")" .

Main = <s> String.