Bertram Ludäscher Rainer Himmeröder Georg Lausen Wolfgang May Christian Schlepphorst Managing Semistructured Data with FLORID: A Deductive Object-Oriented Perspective. 589-613 1998 23 Inf. Syst. 8 db/journals/is/is23.html#LudascherHLMS98 http://dx.doi.org/10.1016/S0306-4379(98)00030-1