Integrating relational and object-oriented database systems using a metaclass concept. - Wolfgang Klas; Gisela Fischer; Karl Aberer (J. Syst. Integr., 1994)

Semantic Query Optimization for Methods in Object-Oriented Database Systems. - Karl Aberer; Gisela Fischer (ICDE, 1995)

Admissible Record-Oriented Evaluation Plans for Declarative Updates. - Gisela Fischer; Karl Aberer (ADBIS, 1997)