Thank you for sharing your question! I love the question, “Which fractions should be transcribed as spatial material?”
One good place to start is considering the benefits of spatial layout. (Spoiler: after listing a couple of benefits, we will weigh the benefits against the drawbacks.)
Spatial layout has the benefit of making a direct connection between a label and the specific component that is being labeled.
In addition, spatial layout can pretty closely reproduce the print layout. This can make it easier for a sighted teacher or classmate to discuss content with the braille user.
Now let’s talk drawbacks.
Reading a spatial layout can be a challenging proposition, forcing the braille user to recognize and remember connections both horizontally and vertically simultaneously while also traversing some utterly blank space. Another challenge is that if a label applies to multiple components, a spatial layout can make it seem like it applies only to one.
With that, and a few other things in mind, I might use something like the following criteria to identify which fractions should be transcribed as spatial material:
- Each label in print applies to one component … … or the components to which any label applies can clearly be indicated with two (or maybe three) tactile graphic lead lines
- The text explicitly discusses the spatial nature of the content.
Lastly, remember you can present a fraction twice – once linearly without labels and then again spatially. (This is like what we do with a poem with scansion marks. Braille Formats 2016 §13.9.3)
Please let us know if you need anything more or different!
–Kyle