InhaltsangabeIntroduction: What landmarks are, and why they are important.- Landmarks: A thought experiment.- Cognitive aspects: How people perceive, memorize, think and talk about landmarks.- Conceptual aspects: How landmarks can be described in data models.- Computational aspects: How landmarks can be observed, stored, and analysed.- Communication aspects: How landmarks enrich the communication between human and machine.- Conclusions: What is known and what is still challenging about landmarks.