Relatively recent, still lacking a proper theoretical framework and often considered as interdisciplinary, the "Science of information" remains unfocused. The present article addresses several essential points that could help contribute to a definition: what is the frame of reference of researchers – the "epistemological attitude" of the Science of Information – and what is it really about – what is its "disciplinary specificity"? Where should it be placed in relationship to "Communication science", within the overall schema of Information and Communication Sciences? What could provide its theoretical framework?