The collection of articles in this issue of the Bulletin of the American Society for Information Science and Technology reflects the association between knowledge and the methods we use to represent a knowledge domain – knowledge organization systems (KOS). Though necessary and beneficial, our efforts to capture and represent knowledge impose a structure and inevitably reflect our perceptions and established notions. We must be aware of limits created in the process and be open to innovative approaches that facilitate access and serve all users without operational or cultural barriers. These collected articles explore new ideas in developing KOS designs and in their structural frameworks. They describe real world projects that illustrate innovations and challenge conventional approaches to knowledge organization systems.