Most existing knowledge organization systems (KOS) are based on disciplines. However, as research is increasingly multidisciplinary, scholars need tools allowing them to explore relations between phenomena throughout the whole spectrum of knowledge. We focus on the dependence relationship, holding between one phenomenon and those at lower integrative levels on which it depends for its existence, like alpinism on mountains, and mountains on rocks. This relationship was first described by D.J. Foskett in the context of CRG's work towards a non-disciplinary scheme. We discuss its possible status and representation in three kinds of KOS: thesauri, classification schemes, and ontologies. In thesaural structures, dependence could be one of the subtypes of associative relationships (RT) which have been wished to enrich their semantic functions. In classification, it could act together with hierarchy as a structuring principle, providing a way of connecting and sorting main classes based on integrative levels. In ontologies, it could be defined as a dependsOn direct slot, expressing the fact that through it a class does not inherit all properties of the other class on which it depends. We argue that providing search interfaces with cross-disciplinary links of this kind can give users more adequate tools to examine the recorded knowledge through creative paths overcoming some limitations of its canonical segmentation into disciplines.