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Also take a look at the Boom Hierarchy [1], which came from the same era (Bird-Meertens formalism, etc.). It describes relationships between data structures constructed from 4 algebraic properties: unit, commutative, associative and idempotent. The resulting 16 possibilities include the familiar set, bag, list and tree, but also other less useful combinations, such as non-empty mobile.

[1] http://citeseerx.ist.psu.edu/viewdoc/download?doi=

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