: A large number of ontologies have been introduced by the biomedical community in recent years. From an application perspective, identifying related ontologies and linking them together is an important goal of research. In order to achieve this, it is essential to analyze how similar concepts are specified in different ontologies. In addition, it is important to understand how ontologies as a whole overlap and how they could be clustered based on the relationships between them. There is an urgent need for a mechanism to build interoperability between the growing number of ontologies developed by different groups. This paper reviews the challenges in defining overlapping relationships in the Open Biomedical Ontologies (OBO), analyzes aspects of overlapping relationships between them and provides an interoperability framework, called InterOBO, for sharing biomedical knowledge across OBO communities.