Like mentioned previously, using the MetadataStore:
i.e.
var span1 = new EntitySpan(typeof(Employee), EntityRelations.FK_Order_Employee, EntityRelations.FK_OrderDetail_Order);
var span1 = new EntitySpan(typeof(Employee), EntityMetadataStore.Instance.GetEntityRelation(typeof(Employee), Employee.EntityPropertyNames.Orders), EntityMetadataStore.Instance.GetEntityRelation(typeof(Order), Order.EntityPropertyNames.OrderDetails));
Silvio.