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1971, Information and Control
Let d" be a category of input objects and a/a category of output objects. Assume that d" has limits and d has colimits; then, the behavior of every diagram in the category of abstract machines (d', ~¢) over a connected scheme can be recorded in its limit. Thus, the theory of limit preserving functors describes the interconnections between the various traits that the total system exhibits. Hence, "the systems theorist is told" what jobs an arbitrary system can do for the given system.
1971
Information and Computation/information and Control - IANDC, 1983
Lecture Notes in Physics, 2013
We define the category Func Î with functors F:D F¨S COTT (D F´C PO) as objects and pairs (f:D F¨DG ,ú:FÿGºf) as morphisms (ú is a natural transformation). We show that this category is closed under the common domain theoretical operations +,ÿ,÷ and ¨. The category Func Î is an O-category Tennent 1993].
We extend the treatment of algebra automata to automata employing algebras over arbitrary theories. To this end we re-present Eilenberg and Wright's approach to the notion of a theory and its algebras originated by Lawvere. Special attention is given here to the free theories which correspond, in ordinary automata theory, to the free monoids. For example, we prove that the free theories (like the free monoids) are characterized as the projective objects in the category of theories with surj ective morphisms of theories only.
The theory of algebraic specifications-one of the most important mathematical approaches to the specification of abstract data types and software systems-is reviewed from a mathematical and a computer science point of view. The important role of category theory in this area is discussed and it is shown how the following selected problems are treated using category theory: First, a unified framework for specification logics, second compositional semantics, third partial algebras and their specification, and fourth specifications and models for concurrent systems. For the solution of two of the problems classifying categories are used. They allow to present categories of algebras as functor categories and to derive a number of important properties from well known results for functor categories.
Mst, 1973
The paper first shows how the categorical theory of sequences is useful in explaining properties of the (word) differentiation of Brzozowski (1964). Then, the paper shows how a more general theory of languages, including both procedural and functional languages, should be constructed by using a switch proposition that extends the common equivalence between the general tensor and general horn functors of categories. Lastly, the paper offers a new way of approaching projectivity concepts of general relative homological algebra. The most interesting result is that there is a class of functors so that "functor-projectives" intersect projectives and injectives trivially, and behave correctly. Moreover, any non-zero abelian group is not Q®-projective. Introduction. This paper offers a new way, and perhaps more general way, of approaching projectivity concepts of relative homological algebra [4]. The most interesting result is that there is a class of functors so that "functorprojectives" intersect projectives and injectives trivially, and behave correctly. Basic concepts o f group theory come from Rotman [13], while those of category theory come from Mitchell [11]. We begin by reviewing the classical notions from relative projectivity [4].
Annals of Pure and Applied Logic, 2008
We give an introduction to Turing categories, which are a convenient setting for the categorical study of abstract notions of computability. The concept of a Turing category first appeared (albeit not under that name or at the level of generality we present it here) in the work of Longo and Moggi; later, Di Paolo and Heller introduced the closely related recursion categories. One of the purposes of Turing categories is that they may be used to develop categorical formulations of recursion theory, but they also include other notions of computation, such as models of (partial) combinatory logic and of the (partial) lambda calculus. In this paper our aim is to give an introduction to the basic structural theory, while at the same time illustrating how the notion is a meeting point for various other areas of logic and computation. We also give a detailed exposition of the connection between Turing categories and partial combinatory algebras and show the sense in which the study of Turing categories is equivalent to the study of PCAs.
2012
These are brief informal notes based on lectures I gave at McGill. There is nothing original about them.
arXiv (Cornell University), 2023
We study bicategories of (deterministic) automata, i.e. how automata E ← E ⊗ I → O organise as the 1-cells of a bicategory Mly K , drawing from prior work of Katis-Sabadini-Walters, and Di Lavore-Gianola-Román-Sabadini-Sobociński, and linking their bicategories of 'processes' to a bicategory of Mealy machines constructed in 1974 by R. Guitart. We make clear the sense in which Guitart's bicategory retains information about automata, proving that Mealy machines a la Guitart identify to certain Mealy machinesà la K-S-W that we call fugal automata; there is a biadjunction between fugal automata and the bicategory of K-S-W. Then, we take seriously the motto that a monoidal category is just a one-object bicategory. We define categories of Mealy and Moore machines inside a bicategory B; we specialise this to various choices of B, like categories, relations, and profunctors. Interestingly enough, this approach gives a way to interpret the universal property of 'reachability of a state' as a Kan extension and leads to a new notion of 1-and 2-cell between Mealy and Moore automata, that we call intertwiners, related to the universal property of K-S-W bicategory.
Lecture Notes of the Institute for Computer Sciences, Social Informatics and Telecommunications Engineering, 2016
Self-* is widely considered as a foundation for autonomic computing. The notion of autonomic systems (ASs) and self-* serves as a basis on which to build our intuition about category of ASs in general. In this paper we will specify ASs and self-* and then move on to consider finite limits and colimits in ASs. All of this material is taken as an investigation of our category, the category of ASs, which we call AS.
2024
[March 28, 2024 version] An update to the early chapters of my earlier Gentle Introduction notes, requiring only modest mathematical background. There are chapters on categories, and on constructions like products, pullbacks, exponentials that can occur in different categories. There is also a first encounter with functors. Part II continues the story, talking about natural transformations between functors, the Yoneda lemma and adjunctions and we take an introductory look at the idea of an elementary topos This book Part I is available as a cheap print-on-demand paperback from mid April, but I think of it as a beta version, still work in progress and all comments are still most welcome.
This paper approaches the question "What is category theory" by focusing on universal mapping properties and adjoint functors. Category theory organizes mathematics using morphisms that transmit structure and determination. Structures of mathematical interest are usually characterized by some universal mapping property so the general thesis is that category theory is about determination through universals. In recent decades, the notion of adjoint functors has moved to center-stage as category theory's primary tool to characterize what is important and universal in mathematics. Hence our focus here is to present a theory of adjoint functors, a theory which shows that all adjunctions arise from the birepresentations of "chimera" morphisms or "heteromorphisms" between objects in different categories. This theory places adjoints within the framework of determination through universals. The conclusion considers some unreasonably effective analogies between these mathematical concepts and some central themes in the life sciences and in social philosophy. This paper is from: What is Category Theory? Edited by Giandomenico Sica, Polimetrica, Milan, 2006.
1. The problem. The phenomenology of living systems (i.e., their relation to the physical world) does not yet have a satisfactory theory. This is not just a philosophical issue. In order to emulate the skill and subtlety of biological computation in our own machines and systems, we need to understand what are the means by which such veridicality is obtained.
A process X: % +% is output if Dyn(X) +% has a right adjoint; state-behavior if Dyn(X) + X has both left and right adjoints; and adjoint if X has a right adjoint and % has countable coproducts. Output processes provide the proper setting for a general theory of state observability. We give a minimal realization theory using image factorization of a total response map. We give an adjointness theory for state-behavior machines and a duality theory for adjoint machines which clarifies classical linear system duality and yields an improved duality for nondeterministic automata. Adjoint machines (machines with adjoint input processes) provide the first integration of classical sequential machines (the only state-behavior machines in the category, Set, of sets), metric machines, topological machines, linear systems, nondeterministic automata and Boolean machines. There exist state-behavior machines which are not adjoint (but not in Set).
Lecture Notes in Computer Science, 1996
The paper summarizes the main concepts and paradigms of category theory and explores some of their applications to the area of algebraic speci cations. In detail we discuss di erent approaches to an abstract theory of speci cation logics. Further we present a uniform framework for developing particular speci cation logics. We make use of`classifying categories', to present categories of algebras as functor categories and to obtain necessary basic results for particular speci cation logics in a uniform manner. The speci cation logics considered are: equational logic for total algebras, conditional equational logic for partial algebras, and rewrite logic for concurrent systems. Category theory arose from the fundamental idea of representing a function by an arrow. This idea rst appeared in topology about 1940 (see Mac71]). The orig-' Funct PROD AT(Colim j SPEC j); SET ] ' Funct PROD Colim j AT(SPEC j); SET ] ' Lim j Funct PROD AT(SPEC j); SET ] ' Lim j Mod(SPEC j) Let's sum up the results for SET {models for the general approach as
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