The classical Nevanlinna-Pick (NP) interpolation problem is about finding a rational function that satisfies given interpolation conditions, along with a norm condition. In this paper we address the NP problem using concepts from behavioral systems theory and quadratic differential forms (QDFs). The NP problem is solved using a certain “dualization of data”. We address system theoretic motivations for this dualization and the advantages gained in this process. Finally, we address the problem of constructing interpolating functions that satisfy a “frequency dependent” norm condition
