In this paper, we present the ADORA approach to object-oriented modeling of software (ADORA stands for Analysis and Description of Requirements and Architecture). The main features of ADORA that distinguish it from other approaches like UML are the use of abstract objects (instead of classes) as the basis of the model, a systematic hierarchical decomposition of the modeled system and the integration of all aspects of the system in one coherent model. The paper introduces the concepts of ADORA and the rationale behind them, gives an overview of the language, and reports the results of a validation experiment for the ADORA language.