anchor.diff:        };
         model_widget.graphic[0].data('set', model_widget.graphic)
         model_widget.graphic[0].drag(move, start);
  +      addRelationships(model_widget);
   
         model_widgets.push(model_widget);
       });
  
positive.code:           r.text(60 + 30, 40 + 20, model.name)
          )
        };
  
        model_widgets.push(model_widget);
      }
  
negative.code:     relationship.destination.relationships.push(relationship);
    });
  
    function centerOf(element) {
      return [element.attr('x') + element.attr('width') / 2, element.attr('y') + element.attr('height') / 2];
    }
  
    function modelWidgetForModel(model) {
      return _.find(model_widgets, function(model_widget) {return model_widget.model == model});
    }
  
    function otherModel(model, relationship) {
      if (relationship.source == model) {
        return relationship.destination;
      }
      else {
        return relationship.source;
      }
    }
  
    function addRelationships(model_widget) {
      var srcCenter = centerOf(model_widget.graphic[0]);
      _.each(model_widget.model.relationships, function(relationship) {
        om = otherModel(model_widget.model, relationship);
        modelWidget = modelWidgetForModel(om);
        console.log(modelWidget);
        if (modelWidget) {
          var destCenter = centerOf(modelWidget.graphic[0]);
          path = r.path("M" + srcCenter[0] + ',' + srcCenter[1] + 'L' + destCenter[0] + ',' + destCenter[1])
        }
      });
    }
  
    function start(x, y, ev) {
        this.ox = this.attr('x');
        this.oy = this.attr('y');
  