diff --git a/dune/mmdg/problems/dgproblem.hh b/dune/mmdg/problems/dgproblem.hh
index c7ffb3d239d627d0ab76f648b316eb1d658fb416..f8d22f3f88daa7fbf2c1dc2b222e37a26e335017 100644
--- a/dune/mmdg/problems/dgproblem.hh
+++ b/dune/mmdg/problems/dgproblem.hh
@@ -9,6 +9,8 @@ class DGProblem
   public:
     using Scalar = ctype;
     using Vector = Coordinate;
+    static constexpr int dimension = Coordinate::dimension;
+    using Matrix = Dune::FieldMatrix<Scalar, dimension, dimension>;
 
     //the exact solution at position pos
     virtual Scalar exactSolution (const Vector& pos) const
@@ -22,14 +24,14 @@ class DGProblem
       return false;
     };
 
-    //source term
-    virtual Scalar q (const Vector& pos) const //= 0;
+    //source term at position pos
+    virtual Scalar q (const Vector& pos) const
     {
       return Scalar(0.0);
     }
 
     //boundary condition at position pos
-    virtual Scalar boundary (const Vector& pos) const //= 0;
+    virtual Scalar boundary (const Vector& pos) const
     {
       return Scalar(0.0);
     }
@@ -40,6 +42,20 @@ class DGProblem
     {
       return 1;
     }
+
+    //permeability tensor at position pos
+    virtual Matrix K (const Vector& pos) const
+    {
+      Matrix permeability(0.0);
+
+      for (int i = 0; i < dimension; i++)
+      {
+        permeability[i][i] = 1.0;
+      }
+
+      //return identity matrix
+      return permeability;
+    }
 };
 
 #endif