// Dag.h - wdg - 2008
#ifndef DAG_H
#define DAG_H

//DAG is Directed Acyclic Graph
#include<string>
using namespace std;

class DAG 
{
  public:
    virtual void addEdge (int u, int v) = 0;
    virtual void removeEdge(int u, int v) = 0;
    virtual bool isAdjacent (int u, int v) const = 0;
    virtual int outDegree(int u) const  = 0;
    virtual int inDegree(int u) const = 0;
    virtual int numberEdges() const = 0;
    virtual int numberVertices() const = 0;
    virtual string toString() const = 0;
};

#endif