Abstract-One of the major challenges in the emerging interdisciplinary field of human-computer interaction (HCI) is the specification of a research line that can enable the development of validated design knowledge with a predictive power for the design of interactive systems. Based on the three different elements in the design of interactive systems: (1) human being(s), (2) technical artefact(s), and (3) context of use, different academic disciplines contribute with different research paradigms to this new field: social sciences with a strong empirical and experimental approach, industrial and interaction design with a strong emphasis on artistic design, and engineering disciplines with a strong technical and formal approach. This programmatic paper presents, discusses and recommends a possible way to integrate the strengths of different research and design paradigms based on triangulation, and we argue for HCI as an engineering discipline.Index Terms-human computer interaction, design paradigm, research agenda, triangulation.