This paper aims to give a feeling of the roles that discipline-oriented subject classifications can play in the Open Archive movement for the free dissemination of information in research activities. Mathematics, and Mathematics Subject Classification, will be the focuses around which we will move to discover a variety of presentation modes, protocols and tools for human and machine interoperability. The Open Archives Initiative (OAI) is intended to be the effective framework for such a play. In the first part of this paper, we start by describing the most important subject classification schemes in mathematics and related disciplines. Then we sketch the structure of discipline-oriented schemes in view of browsing and we give an account of different browsing modalities, implemented in the tools we produced and collected in The Scientific Classifications Page. Finally we give an insight on the design, implementation and use of a programming language for the generation of hypertextual presentations of complex structured data. In the second part, we list different strategies for e-print communication in scientific research, up to the basic definitions of the Open Archives Initiative. A review of the functionalities actually implemented in OAI compatible archives managed by the EPrints software will lead us to some working hypotheses about the roles that subject classifications in mathematics and related disciplines can play in the scenarios of the Open Archives movement.