Chapter 5 Figures-Channel Ambiguity Analysis
This appendix presents the five-dimensional ambiguity analysis of the SDA Design Standard (2019) figures channel as implemented by the serialisation schema evaluated in Chapter 5. The analysis covers the full 406-entry serialised figures corpus and reports the proportion of ambiguity dimensions resolved by the schema relative to those present in the source material, together with interpretation of residual ambiguity in each dimension. The complementary text-channel evaluation is documented in Appendix: Chapter 5 Evaluation Results and Data Package. Source data: ambiguity-delta-figures.json and parity-deepening-statistics.json (run_id 2603241227), archived in the data package at publish-thesis/publish-data/appendix-data/ch5-artefact-bundle/data-package/canonical/.
Five-Dimensional Ambiguity Model
The ambiguity-delta metric is computed across five orthogonal dimensions, each capturing a distinct facet of interpretive uncertainty in normative standards text. Each dimension is scored as a binary per entry: present (the dimension is relevant to the entry), resolved (the schema eliminates the ambiguity), or residual (the ambiguity persists despite serialisation).
Identity ambiguity — whether the subject entity of a requirement can be unambiguously identified.
Structural ambiguity — whether the syntactic decomposition of a requirement into subject-predicate-object triples is deterministic.
Deontic ambiguity — whether the modal force (obligatory, permissive, prohibitive) of a requirement is unambiguously classifiable.
Dimensional ambiguity — whether quantitative values attached to a requirement are fully specified.
Categorical ambiguity — whether the SDA design categories to which a requirement applies are explicitly determined.
Per-Dimension Results
The overall ambiguity-delta across the figures corpus is 0.9148, indicating that 91.48% of all ambiguity-bearing dimensions are resolved through the serialisation process. The per-dimension results are presented in the following table.
Table A5-FA.1: Figures-channel ambiguity-delta by dimension
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Source: ambiguity-delta-figures.json, global_dimension_summary (run_id 2603241227).
Two dimensions achieve full resolution; one achieves near-perfect resolution; two dimensions carry characterised residual ambiguity. The pattern is structurally predictable and reflects properties of the source standard rather than limitations of the schema design. In summary, the five-dimensional profile establishes a clear resolution hierarchy that the next sections document in detail, proceeding from perfect-resolution dimensions through near-perfect resolution to the two dimensions where characterised residual ambiguity remains.
Perfect-Resolution Dimensions
Identity ambiguity is resolved at 100.00% across 174 instances. This outcome reflects the entity-resolution pipeline’s capacity to canonicalise variant surface forms into a controlled vocabulary of 56 unique canonical entities. The 100% resolution rate confirms that every entity referenced in the design requirement entries of the serialised corpus can be unambiguously traced to a single canonical identifier. This is a non-trivial outcome: the source standard deploys 20 distinct surface variants for the entity Door alone — ranging from “Door circulation spaces” to “required internal door circulation space” — yet the schema resolves all of them to the canonical subject without information loss.
Deontic ambiguity is likewise resolved at 100.00% across all 205 modal entries. The modal term inventory recovered from the corpus comprises six distinct markers: “shall” (200 occurrences), “is permitted” (7), “may” (4), “are permitted” (2), “shall not” (2), and “not permitted” (1). Zero entries were flagged as deontic-ambiguous, meaning every requirement with modal content could be assigned to exactly one of the three force classes (obligatory, permissive, prohibitive) without adjudication. The absence of deontic ambiguity is partly attributable to the SDA standard’s disciplined use of “shall” as its obligatory marker — a convention that, while not universally observed in Australian standards drafting, is sufficiently consistent in this instrument to permit automated classification. This implies that automated deontic tagging is fully feasible for this corpus without any manual adjudication phase. The next section documents the single residual in the structural dimension.
Near-Perfect Resolution: Structural
Structural ambiguity is resolved at 99.47%, with 188 of 189 design requirements successfully decomposed into subject-predicate-object triples. The decomposition quality audit reports 187 clean decompositions (98.9%), 1 fallback decomposition (0.5%), and 1 failed decomposition (0.5%). The single failed entry is ID 235, sourced from Figure 10: “Use of shower screens is not permitted.” This entry resists triple decomposition because its syntactic structure is a bare prohibition without a clear spatial predicate — the prohibition applies to an entire class of objects rather than to a spatial relationship. The schema records this as a tracked residual rather than discarding the entry, preserving the normative content while acknowledging the structural limitation.
Residual Ambiguity: Dimensional
Dimensional ambiguity is resolved at 88.74%, with 17 residuals across 151 dimensionally-active entries. The residual rate of 12.26% arises from two distinct mechanisms. First, some entries specify dimensional ranges rather than point values (for example, “900 mm to 950 mm based on design category”), where the precise applicable dimension depends on the SDA category context. The serialisation schema captures the range but cannot collapse it to a single value without category resolution. Second, entries referencing external standards (for example, “as per AS1428.1”) inherit dimensional requirements that are not reproduced within the SDA standard’s own text or figures. These external references constitute genuine residual ambiguity from the perspective of the SDA corpus alone: a practitioner must consult the referenced instrument to determine the applicable dimension.
The 17 dimensional residuals are concentrated in the Design requirement field type, where the class profile reports an average ambiguity delta of 0.949 — still high, but acknowledging that approximately one in six dimensionally-active requirements carries some unresolved quantitative specification. This finding has direct implications for automated compliance checking, where dimensional completeness is a prerequisite for programmatic verification. Building on this characterisation of dimensional residuals, the next section addresses categorical ambiguity, which presents the largest residual proportion of the five dimensions.
Residual Ambiguity: Categorical
Categorical ambiguity presents the lowest resolution rate at 72.84%, with 63 residuals out of 232 categorically-active entries. The 63 residuals divide into two structural sources with distinct interpretations.
The first source accounts for 43 residuals (68.3% of categorical residuals) and originates in the Note field type. Notes in the serialised corpus carry categorical tagging (all 43 Note entries are categorically-active) but none are categorically-resolved, producing a categorical resolution rate of 0.0% within Notes. This is by design: notes are informational glosses that contextualise requirements without themselves being category-specific obligations. The schema correctly identifies categorical presence (notes apply within a categorical context) while marking resolution as impossible (notes do not prescribe for a specific category).
The second source accounts for 20 residuals and originates in the Design requirement field type, where 189 categorically-active entries resolve to 169 with 20 residuals. These 20 residuals arise from requirements that span multiple categories with category-dependent dimensional variation — the polysemy cases documented in Appendix: Polysemy Metrics and Confidence. For instance, the entity Door carries a minimum clear opening of 820 mm for Improved Liveability and Robust categories, 900 mm for Fully Accessible, and 950 mm for High Physical Support. The schema serialises each variant but cannot collapse the requirement to a single category without losing the category-contingent dimensional specification. Taken together, the two categorical residual sources account for all 63 unresolved cases in a fully characterised manner, with no unclassified residuals.
Implications for Standards Interpretation
The 91.48% overall resolution rate demonstrates that a structured serialisation schema can eliminate the vast majority of interpretive ambiguity in a building standards instrument. The residual ambiguity is not randomly distributed but is concentrated in two predictable and well-characterised zones: categorical indeterminacy in notes (a genuine semantic property of informational text) and dimensional-categorical coupling (where the same spatial requirement takes different quantitative values depending on the SDA design category). Both forms of residual ambiguity are tracked rather than hidden: the schema flags them explicitly, enabling downstream consumers to route these cases to human adjudication or category-specific lookup tables.
Identity, structural, and deontic ambiguity are resolved at or near 100%. These results establish that the serialisation schema provides a reliable foundation for automated triple extraction. Category-contingent dimensional specification remains inherently complex, but the schema acknowledges this explicitly. Overall, the 91.48% aggregate resolution rate confirms that the schema meets the performance threshold for Chapter 5 evaluation claims. Characterised residuals provide the transparency needed for downstream consumers to route unresolved cases to appropriate adjudication mechanisms.