Abstract

This article examines the diagram as a critical cognitive and communicative tool within Service Design methodologies, focusing in particular on the Double Diamond model. It opens with a review of conventional practices in service design—such as desk and field research, participatory methods, and visual tools including personas, blueprints, and experience maps—and critiques their partial and often fragmented integration into existing diagrammatic models. Through a comparative analysis of the Double Diamond and several emerging alternatives (Zendesk Triple Diamond, Design Odyssey, and Open-Cycle), the study identifies key structural limitations: the rigidity of phase transitions, the oversimplification of iterative processes, and the lack of a clearly defined stage for reframing design challenges as a conceptual bridge between research and ideation. Six academic case studies are analyzed to support this proposal, introducing the dimensions of time and complexity as axes for visualizing project dynamics. The study concludes by advocating for diagramming not merely as a form of representation, but as a mode of thinking—one that externalizes insight, synchronizes processes, and supports design pedagogy. This approach encourages more adaptive, comparative, and pedagogically productive uses of visual frameworks in both the education and the practice of service design.