A survey of concepts for information system specification is given, based on the viewpoint that an information system is a community of interacting objects. Objects are self-contained units of structure and behavior capable of operating independently and cooperating concurrently. The approach integrates concepts from semantic data modeling and concurrent processes, adopting structuring principles partly developed in the framework of object-orientation and partly in that of abstract data types. The languages OBLOG and TROLL are based on these concepts, their use is illustrated by examples.