5 citations · 15 across the 7 of their papers we have counts for
9 papers
Ordered Ehresmann semigroups and categories
Tim Stokes
Ehresmann semigroups may be viewed as biunary semigroups equipped with domain and range operations satisfying some equational laws. Motivated by some of the main examples, we here…
Restriction in Program Algebra
Marcel Jackson, Tim Stokes
We present axiomatisations for a number of partial function signatures that include domain restriction, modelled as a right normal band operation. Other operations considered are o…
Override and restricted union for partial functions
Tim Stokes
The {\em override} operation is a natural one in computer science, and has connections with other areas of mathematics such as hyperplane arrangements. For arbitrary funct…
Constellations with range and IS-categories
Victoria Gould, Tim Stokes
Constellations are asymmetric generalisations of categories. Although they are not required to possess a notion of range, many natural examples do. These include commonly occurring…
Left restriction monoids from left -completions
Tim Stokes
Given a monoid with any non-empty subset of its idempotents, we present a novel one-sided version of idempotent completion we call left -completion. In general, the cons…
The algebra of non-deterministic programs: demonic operators, orders and axioms
Robin Hirsch, Szabolcs Mikulás, Tim Stokes
Demonic composition, demonic refinement and demonic union are alternatives to the usual "angelic" composition, angelic refinement (inclusion) and angelic (usual) union defined on b…
Override and update
Marcel Jackson, Tim Stokes
Override and update are natural constructions for combining partial functions, which arise in various program specification contexts. We use an unexpected connection with combinato…
Constellations and their relationship with categories
Victoria Gould, Tim Stokes
Constellations are partial algebras that are one-sided generalisations of categories. It has previously been shown that the category of inductive constellations is isomorphic to th…
Monoids with tests and the algebra of possibly non-halting programs
Marcel Jackson, Tim Stokes
We study the algebraic theory of computable functions, which can be viewed as arising from possibly non-halting computer programs or algorithms, acting on some state space, equippe…