Graph notation as a gateway—transitioning from causal loop to stock and flow diagrams (and beyond) in system dynamics modeling

Abstract

This study addresses the gap between causal loop diagrams (CLDs) and stock and flow diagrams (SFDs) in system dynamics modeling. While the ambiguity of standard CLDs eases early stakeholder engagement, it hinders precise simulation model building in later stages. Building on prior link- and node-labeling approaches, we introduce CLD+, an enhanced yet intuitive notation that explicitly marks variable types, distinguishes material from information links, and treats delays/subsystems as first-class nodes. With these annotations, a CLD+ is structurally equivalent to an SFD: it can be transformed automatically into an SFD or quantified directly as a simulation model, making CLD+ not only a bridge but a full-fledged surrogate for SFDs. We discuss implications for tooling that supports round-trip conversion and ‘store-once-use-everywhere’ workflows, reducing transition costs and improving model reliability in practice and education.