Website Link: https://www.johnbiggs.com.au/academic/solo-taxonomy/

SOLO Taxonomy is a means of classifying learning outcomes in terms of their complexity, enabling us to assess students’ work in terms of its quality.
5 Levels of SOLO Taxonomy
1. Prestructural
2. Unistructural
3. Multistructural
4. Relational
5. Extended Abstract
Poster of SOLO Taxonomy

SOLO can be used not only in assessment, but in designing the curriculum in terms of the level of learning outcomes intended, which is helpful in implementing constructive alignment.
Applying The Taxonomy To Various Teaching Subjects
https://books.google.co.nz/books?id=xUO0BQAAQBAJ&pg=PA33&source=gbs_toc_r&cad=3#v=onepage&q&f=false