Spans in 2-Categories: A monoidal tricategory

Understand

We present Trimble's definition of a tetracategory and prove that the spans in (strict) 2-categories with certain limits have the structure of a monoidal tricategory, defined as a one-object tetracategory.

• We recall some notions of limits in 2-categories for use in the construction of the monoidal tricategory of spans.