///<summary>
 ///relationship of joined parts
 ///</summary>
 public void setRelationship(Relationship pRelationship)
 {
     _relationship = pRelationship;
 }
        /**
         * Compares for reference equality and value equality.
         */
        public bool equals(Relationship rhs)
        {
            bool ivarsEqual = true;

            if(rhs.GetType() != this.GetType())
                return false;

            if( ! (_nature == rhs._nature)) ivarsEqual = false;
            if( ! (_position == rhs._position)) ivarsEqual = false;

            return ivarsEqual;
        }