The algebraic specification of abstract data types is now awell establishedresearch topic in computer science. Thisarea influences both applications and theoreticalfoundations of methodologies which support the design andformal development of reliable software. The Seventh Workshop on Specification of Abstract Data Typestook place in Wusterhausen/Dosse, April17-20, 1990, and wasorganized in cooperation with the ESPRIT Basic ResearchWorking Group COMPASS. The main topics covered by theworkshop were:- Modularization- Object orientation- Higher-order types anddependent types- Inductive completion- Algebraic high-level nets.