Discussion: WCAG 2.1 Conformance of Small Multiple (Multi-Panel) Scientific Figures

Hello WAI Interest Group,

I'd like to raise a topic that I believe affects many scientific and
data-driven organizations but lacks clear WCAG guidance: the accessibility
conformance of "*small multiple*" figures.

For those unfamiliar, a *small multiple* (a term popularized by Edward
Tufte) is a series of small, simplified graphs arranged in a grid layout so
that viewers can compare trends across all panels simultaneously. Here are
some public references:
- Juice Analytics overview:
https://www.juiceanalytics.com/writing/better-know-visualization-small-multiples
- Wikipedia overview: https://en.wikipedia.org/wiki/Small_multiple
- U.S. federal data visualization standards:
https://xdgov.github.io/data-design-standards/components/small-multiples
- CDC COVE small multiples guidance:
https://www.cdc.gov/cove/data-visualization-types/small-multiples.html

This is a foundational visualization technique in scientific publishing,
public health, economics, climate science, and many other fields.

The Problem I Encountered:
In a scientific publishing context, a figure consisting of 12 panels in a
3×4 grid was created for comparative trend analysis. The figure is a raster
image (JPG), spans the full width of the page content area (1140px), and
scales responsively on desktop and mobile devices. During an accessibility
evaluation, the evaluator recommended separating the figure into 12
individual enlarged images, each with its own long description.

I believe this defeats the figure's purpose. The analytical value of a
small multiple depends on the spatial arrangement — viewers scan across
panels to perceive patterns. Each panel is intentionally simplified and
smaller than a standalone chart because you are not meant to examine one
panel in isolation. Breaking it apart is like cutting a map into pieces and
stacking them.

The figure already has: alt text, a detailed figure caption, a long
description summarizing trends across all panels, an accompanying data
table, sufficient contrast and resolution, and responsive design.

The Guidance Gap:
I've searched the WCAG 2.1 Understanding documents, Techniques, and WAI
Tutorials extensively. The closest example is the SC 1.1.1 "data chart"
example — but it describes only a single bar chart. There is no documented
example or guidance for multi-panel composite figures like small multiples.

My interpretation is that:
- SC 1.1.1 Situation B applies: treat it as a complex image, provide short
+ long text alternatives and a data table
- SC 1.4.10 Reflow exception applies: the matrix layout is essential to
meaning, similar to maps and diagrams
- SC 1.4.4 is met: text labels are legible at 200% zoom, and system-level
assistive technology zoom provides additional access

But because there is no documented precedent for this specific image type,
evaluators may reasonably interpret the absence of an example as
non-conformance.

Questions for the Community:
- Has anyone else encountered this issue with small multiples or
multi-panel scientific figures during accessibility evaluations?
- How have you handled it? Did you keep the figure intact or split it apart?
- Does anyone have experience with WCAG conformance assessments of complex
scientific visualizations more broadly?
- Would it be valuable to propose that the AGWG add guidance or an example
addressing this visualization type?

I have also submitted a formal clarification request to
public-agwg-comments@w3.org on this topic.

I'd welcome any perspectives, experiences, or guidance.

Thank you,
Godwin