A coalgebraic, equational approach to the specification of observational structures allowing for a choice in the result type of observations is presented. Observers whose result type is structured as a coproduct of basic types are considered, and notions of covariable, coterm and coequation, dual to the algebraic notions of variable, term and equation are used to specify the associated structures. A sound and complete deduction calculus for reasoning about observational structures is then formulated. Finally, the approach is extended in order to account for the availability of a fixed data universe in the specification of such structures. © 2002 Elsevier Science B.V. All rights reserved.
Crstea, C. (2002). A coalgebraic equational approach to specifying observational structures. In Theoretical Computer Science (Vol. 280, pp. 35–68). https://doi.org/10.1016/S0304-3975(01)00020-2