Different organizations or organizational units are likely to store and maintain different types of information about their software architectures. This inhibits effective management of architectural knowledge. We experimented with a model of architectural knowledge to characterize the use of architectural knowledge in four different organizations. Based on this experimentation we identified four perspectives on architectural knowledge management, and additionally adjusted the model to better align theory with practice. The refined model defines a minimal set of concepts with supposedly complete coverage of the architectural knowledge domain. Because of the minimalistic aspect of the model, we refer to it as a ‘core model’ of architectural knowledge. Supporting evidence for the validity of our model, i.e. the supposed complete coverage, has been obtained by an attempt to falsify this claim through a comparison with selected literature. Application of the core model to characterize the use of architectural knowledge indicates possible areas of improvement for architectural knowledge management in the four organizations.