Chapter 5 Cross-Channel Validation Results

The cross-channel validation analysis for Chapter 5 establishes the complementarity and non-redundancy of the text and figures channels of the SDA Design Standard (2019). The analysis matches figure-derived design requirement triples against text-derived design requirements to classify each figure triple by the degree to which it is confirmed, corroborated, or unmatched in the text channel. The core evaluation claim — that the two-channel architecture is warranted by measurable complementarity rather than by convenience — is grounded in these results. Source data: text-figure-cross-validation.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/.

Match Type Distribution

The bidirectional cross-validation produces a three-way match-type classification by comparing each of the 189 figure-based design requirement triples against the 140 text-based design requirements extracted from the standard’s clause structure. Matching employed both concept matching (entity-name overlap) and dimension matching (shared quantitative values) to classify each figure triple into one of three match types.

Table A5-CC.1: Cross-validation match type distribution

Source: text-figure-cross-validation.json, summary.match_types (run_id 2603241227).

The most consequential finding is that 73 figure-based triples (38.6%) are classified as figure_only — they carry design requirements that exist exclusively in the figure channel with no recoverable textual counterpart. These are not layout details or graphical annotations; they are dimensioned, deontic requirements with subject-predicate-object structure and obligatory modal force. A practitioner or compliance system relying solely on the text clauses of the SDA standard would miss 38.6% of the figure-originated normative content. In summary, the figure-only classification rate is not a marginal residual but a primary structural characteristic of the standard that must inform every downstream compliance system design decision.

The 77 concept-matched triples (40.7%) are defined as figure triples that share entity-level vocabulary with text requirements but lack dimensional confirmation. The text channel acknowledges the existence of the entity and some associated requirement, but the specific dimensional values prescribed in the figure are not reproduced in the text. For example, a text clause may reference “gate clearances” in general terms while the figure specifies the exact 820 mm minimum opening width. The concept match confirms thematic alignment without dimensional parity.

The 39 dimension-matched triples (20.6%) provide the strongest form of cross-channel confirmation: both the entity reference and at least one dimensional value appear in both channels. These cases provide the highest confidence that the figure and text channels encode the same normative intent, albeit often with different levels of specificity.

Directional Asymmetry

The cross-validation establishes a pronounced directional asymmetry between the two channels. Of the 140 text-based design requirements, only 19 (13.6%) have a confirmed figure-based match. The remaining 121 text-based requirements (86.4%) exist only in the text channel. This asymmetry is not symmetrical with the figure-only finding: while 38.6% of figure triples lack textual counterparts, 86.4% of text requirements lack figure counterparts.

This directional pattern is structurally explicable. The text channel of the SDA standard covers a broader regulatory scope — including procedural requirements, cross-references to external standards, and conditional applicability rules — that are not amenable to diagrammatic representation. The figure channel, by contrast, concentrates on spatial and dimensional requirements that benefit from graphical expression. The result is that the two channels are complementary rather than redundant: the text channel carries procedural and conditional content, while the figure channel carries spatial-dimensional content, with a narrow overlap zone of approximately 19 shared requirements. Overall, the directional asymmetry confirms that neither channel is derivable from the other, and that any compliance system must treat both as primary rather than treating either as a derivative supplement. The next section examines the design implications for schema architecture that follow from this structural finding.

Implications for Schema Architecture

The cross-validation results establish that neither channel is a subset of the other. A practitioner relying exclusively on the text channel would miss 38.6% of the figure-originated normative content. A practitioner relying exclusively on the figure channel would miss 86.4% of the text-originated normative content. Only a two-channel extraction architecture that processes both sources and integrates their outputs into a unified triple store can claim to represent the full normative scope of the SDA Design Standard.

These results establish the warrant for the design decision to develop parallel serialisation pipelines for the text and figures channels rather than extracting from one channel alone. The figures-only requirements (73 triples) include specifications for fundamental accessibility features — door opening widths, ramp landing dimensions, bathroom fixture clearances — whose omission from a compliance system would constitute a material failure of the regulatory representation.

The 19 dimension-matched triples also provide an important verification function. Their presence confirms that the two extraction pipelines, operating independently on different source modalities (text versus figure diagrams), converge on the same normative content for a subset of requirements. This convergence provides an internal consistency check on the extraction methodology that does not require external ground truth. Taken together, these three match-type findings — 38.6% figure-only, 40.7% concept-matched, and 20.6% dimension-matched — establish that the two channels are genuinely complementary rather than partially overlapping duplicates, and therefore that the two-channel architecture is the minimal design sufficient to capture the full normative scope of the standard. This establishes the evidentiary basis for the schema design decisions in Chapter 5 and the reproducibility verification procedures documented in the companion data package appendix.