Information exchange is the object of intensive research from quite separated communities, dealing for instance with connected objects, interoperability of industrial information systems, personal information systems or data security. A unified framework, defining the conditions of interrelations of elementary information systems, could allow to address these problems with a holistic view. In that purpose, we suggest the concept of Singular Information System (SIS) and give the basic principles allowing the connection of two SIS. We show then how exchanges of information between objects, persons and organizations may benefit from such a unified paradigm.