Assessing Public Open Space Quality: Explaining Divergence Across Assessment Tools

Public open space (POS) assessment tools have proliferated across disciplines and application contexts, yet their results often remain difficult to compare. Existing research has largely attributed this divergence to differences in indicator selection, overlooking the broader assessment architecture within which indicators acquire meaning. This study examines why POS assessment tools diverge by conceptualizing them as layered socio-technical sign systems. A systematic literature review identified 38 POS assessment tools, which were analyzed through structured content analysis. Twenty empirically derived attributes were mapped to a five-level semiotic framework comprising the empiric, syntactic, semantic, pragmatic, and social levels. The findings demonstrate that divergence is systematic rather than incidental and extends well beyond indicator content. At the empiric level, 57.9% of tools lack complete operational definitions, while 55.3% rely exclusively on subjective indicators. Structurally, 55.3% function as assessment frameworks rather than fully operational tools, reflecting substantial variation in procedural closure. Across all five semiotic levels, the cumulative interaction of measurement practices, structural organization, conceptual framing, intended application and institutional context generates cross-level structural misalignment that fundamentally constrains comparability. In response, this study proposes a semiotic compliance framework that specifies minimum documentation requirements for improving transparency, internal coherence, and interpretability without prescribing indicator standardization. The findings demonstrate that meaningful comparisons among POS assessment tools depend less on reducing indicator diversity than on explicitly aligning and documenting the multiple semiotic layers through which assessment systems generate meaning and support decision-making. The framework provides practical guidance for developing, evaluating, selecting, and comparing future POS assessment tools while preserving the contextual diversity required across different planning and governance settings.