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Monads Need Not Be Endofunctors
"... Abstract. We introduce a generalisation of monads, called relative monads, allowing for underlying functors between different categories. Examples include finitedimensional vector spaces, untyped and typed λcalculus syntax and indexed containers. We show that the Kleisli and EilenbergMoore constr ..."
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Cited by 11 (2 self)
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Abstract. We introduce a generalisation of monads, called relative monads, allowing for underlying functors between different categories. Examples include finitedimensional vector spaces, untyped and typed λcalculus syntax and indexed containers. We show that the Kleisli and EilenbergMoore constructions carry over to relative monads and are related to relative adjunctions. Under reasonable assumptions, relative monads are monoids in the functor category concerned and extend to monads, giving rise to a coreflection between monads and relative monads. Arrows are also an instance of relative monads. 1
Coalgebraic Components in a ManySorted Microcosm
"... Abstract. The microcosm principle, advocated by Baez and Dolan and formalized for Lawvere theories lately by three of the authors, has been applied to coalgebras in order to describe compositional behavior systematically. Here we further illustrate the usefulness of the approach by extending it to a ..."
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Abstract. The microcosm principle, advocated by Baez and Dolan and formalized for Lawvere theories lately by three of the authors, has been applied to coalgebras in order to describe compositional behavior systematically. Here we further illustrate the usefulness of the approach by extending it to a manysorted setting. Then we can show that the coalgebraic component calculi of Barbosa are examples, with compositionality of behavior following from microcosm structure. The algebraic structure on these coalgebraic components corresponds to variants of Hughes’ notion of arrow, introduced to organize computations in functional programming. 1
Traces for Coalgebraic Components
 MATH. STRUCT. IN COMP. SCIENCE
, 2010
"... This paper contributes a feedback operator, in the form of a monoidal trace, to the theory of coalgebraic, statebased modelling of components. The feedback operator on components is shown to satisfy the trace axioms of Joyal, Street and Verity. We employ McCurdy’s tube diagrams, an extension of sta ..."
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This paper contributes a feedback operator, in the form of a monoidal trace, to the theory of coalgebraic, statebased modelling of components. The feedback operator on components is shown to satisfy the trace axioms of Joyal, Street and Verity. We employ McCurdy’s tube diagrams, an extension of standard string diagrams for monoidal categories, for representing and manipulating component diagrams. The microcosm principle then yields a canonical “inner” traced monoidal structure on the category of resumptions (elements of final coalgebras / components). This generalises an observation by Abramsky, Haghverdi and Scott.
Short Contributions
"... CWI is a founding member of ERCIM, the European Research Consortium for Informatics and Mathematics. CWI's research has a themeoriented structure and is grouped into four clusters. Listed below are the names of the clusters and in parentheses their acronyms. Probability, Networks and Algorithm ..."
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CWI is a founding member of ERCIM, the European Research Consortium for Informatics and Mathematics. CWI's research has a themeoriented structure and is grouped into four clusters. Listed below are the names of the clusters and in parentheses their acronyms. Probability, Networks and Algorithms (PNA) Software Engineering (SEN)
CMCS 2010 Categorifying Computations into Components via Arrows as Profunctors
"... The notion of arrow by Hughes is an axiomatization of the algebraic structure possessed by structured computations in general. We claim that an arrow also serves as a basic component calculus for composing statebased systems as components—in fact, it is a categorified version of arrow that does so. ..."
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The notion of arrow by Hughes is an axiomatization of the algebraic structure possessed by structured computations in general. We claim that an arrow also serves as a basic component calculus for composing statebased systems as components—in fact, it is a categorified version of arrow that does so. In this paper, following the second author’s previous work with Heunen, Jacobs and Sokolova, we prove that a certain coalgebraic modeling of components—which generalizes Barbosa’s—indeed carries such arrow structure. Our coalgebraic modeling of components is parametrized by an arrow A that specifies computational structure exhibited by components; it turns out that it is this arrow structure of A that is lifted and realizes the (categorified) arrow structure on components. The lifting is described using the first author’s recent characterization of an arrow as an internal strong monad in Prof, the bicategory of small categories and profunctors.
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"... In a paper presented here in Paphos at FoSSaCS [1], we introduced a generalization of monads, called relative monads, to analyze monadlike structures where the underlying functor is not an endofunctor. This study was motivated by several examples of direct relevance for programming theory, such as ..."
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In a paper presented here in Paphos at FoSSaCS [1], we introduced a generalization of monads, called relative monads, to analyze monadlike structures where the underlying functor is not an endofunctor. This study was motivated by several examples of direct relevance for programming theory, such as finitedimensional vector spaces, the syntaxes of untyped and simplytyped lambdacalculus, but also the arrow types of Hughes [3], as mathematized by Jacobs et al. [4] (in their weak version without the strength). We showed that the Kleisli and EilenbergMoore constructions generalize to relative monads and are related to relative adjunctions (with the Kleisli category of an arrow type as a relative monad turning out to be the same as a Freyd category in the sense of Power and Robinson [6]—much as in the work of Jacobs et al.). We also showed that, under reasonable assumptions, relative monads are monoids in the functor category concerned and extend to ordinary monads, giving rise to a coreflection between relative monads and ordinary monads. But in programming theory applications, we are often interested in strong monads rather than just monads and the standard concept of an arrow type is also that of a strong arrow type. It is therefore natural to ask whether relativization is possible also for strong monads. In this paper, we study this question and answer it in the affirmative. We introduce the concept of a