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Actor Model Theory
In theoretical computer science, Actor model theory concerns theoretical issues for the Actor model. Actors are the primitives that form the basis of the Actor model of concurrent digital computation. In response to a message that it receives, an Actor can make local decisions, create more Actors, send more messages, and designate how to respond to the next message received. Actor model theory incorporates theories of the events and structures of Actor computations, their proof theory, and denotational models. Events and their orderings From the definition of an Actor, it can be seen that numerous events take place: local decisions, creating Actors, sending messages, receiving messages, and designating how to respond to the next message received. However, this article focuses on just those events that are the arrival of a message sent to an Actor. This article reports on the results published in Hewitt 006 :''Law of Countability'': There are at most countably many events. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Theoretical Computer Science
Theoretical computer science (TCS) is a subset of general computer science and mathematics that focuses on mathematical aspects of computer science such as the theory of computation, lambda calculus, and type theory. It is difficult to circumscribe the theoretical areas precisely. The Association for Computing Machinery, ACM's ACM SIGACT, Special Interest Group on Algorithms and Computation Theory (SIGACT) provides the following description: History While logical inference and mathematical proof had existed previously, in 1931 Kurt Gödel proved with his incompleteness theorem that there are fundamental limitations on what statements could be proved or disproved. Information theory was added to the field with a 1948 mathematical theory of communication by Claude Shannon. In the same decade, Donald Hebb introduced a mathematical model of Hebbian learning, learning in the brain. With mounting biological data supporting this hypothesis with some modification, the fields of n ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Unbounded Nondeterminism
In computer science, unbounded nondeterminism or unbounded indeterminacy is a property of concurrency by which the amount of delay in servicing a request can become unbounded as a result of arbitration of contention for shared resources ''while still guaranteeing that the request will eventually be serviced''. Unbounded nondeterminism became an important issue in the development of the denotational semantics of concurrency, and later became part of research into the theoretical concept of hypercomputation. Fairness Discussion of unbounded nondeterminism tends to get involved with discussions of ''fairness''. The basic concept is that all computation paths must be "fair" in the sense that if the machine enters a state infinitely often, it must take every possible transition from that state. This amounts to requiring that the machine be guaranteed to service a request if it can, since an infinite sequence of states will only be allowed if there is no transition that leads to the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Actor Model (computer Science)
The actor model in computer science is a mathematical model of concurrent computation that treats ''actor'' as the universal primitive of concurrent computation. In response to a message it receives, an actor can: make local decisions, create more actors, send more messages, and determine how to respond to the next message received. Actors may modify their own private state, but can only affect each other indirectly through messaging (removing the need for lock-based synchronization). The actor model originated in 1973. It has been used both as a framework for a theoretical understanding of computation and as the theoretical basis for several practical implementations of concurrent systems. The relationship of the model to other work is discussed in actor model and process calculi. History According to Carl Hewitt, unlike previous models of computation, the actor model was inspired by physics, including general relativity and quantum mechanics. It was also influenced by the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Akinori Yonezawa
is a Japanese computer scientist specializing in object-oriented programming, distributed computing and information security. Being a graduate of the University of Tokyo, Yonezawa has a Ph.D in computer science from MIT in the Actor group at the MIT AI Lab. He currently teaches at the University of Tokyo. He is the designer of ABCL/R, a reflective subset of the first concurrent object-oriented programming language ABCL/1. In November 2009, he was awarded with a Medal of Honour with purple ribbon by the Government of Japan. ''Mainichi Shimbun.'' November 2, 2009 (japanese). He won the Senior |
Eike Best
Eike Best (born 13 March 1951) is a German computer scientist, best known for his contributions to concurrency theory. Early life and education Eike Best was born in Neustadt an der Weinstraße. During his childhood, he lived in Argentina, Germany, and Turkey, where his father worked as high school teacher. Best received a high school diploma from thGerman School of Istanbulin 1969, a Diploma in Computer Science from the Technische Hochschule Karlsruhe in 1974, and a PhD from Newcastle University in 1981 for a dissertation on semantics, verification, and design of concurrent programs, supervised by Peter Lauer and Brian Randell. He habilitated in 1988 at the University of Bonn with a thesis on causal semantics of non-sequential programs. Career and contributions Best was research assistant in Carl Adam Petri's research group at the Gesellschaft für Mathematik und Datenverarbeitung near Bonn (1981–1988), and professor in the Computer Science departments at the University of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Henry Baker (computer Scientist)
Henry Givens Baker Jr. is an American computer scientist who has made contributions in garbage collection, functional programming languages, and linear logic. He was one of the founders of Symbolics, a company that designed and manufactured a line of Lisp machines. In 2006 he was recognized as a Distinguished Scientist by the Association for Computing Machinery. He is notable for his research in garbage collection, particularly Baker's real-time copying collector, and on the Actor model. Baker received his B.Sc. (1969), S.M. (1973), E.E. (1973), and Ph.D. (1978) degrees at M.I.T. The Chicken Scheme compiler Chicken (stylized as CHICKEN) is a programming language, specifically a compiler and interpreter which implement a dialect of the programming language Scheme, and which compiles Scheme source code to standard C. It is mostly R5RS compliant an ... was inspired by an innovative design of Baker's. Bibliography * * * * * References External links Henry Baker's Archive ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Actor Model Implementation
In computer science, Actor model implementation concerns implementation issues for the Actor model. Cosmic Cube The Caltech Cosmic Cube was developed by Chuck Seitz ''et al.'' at Caltech providing architectural support for Actor systems. A significant difference between the Cosmic Cube and most other parallel processors is that this multiple instruction multiple-data machine uses message passing instead of shared variables for communication between concurrent processes. This computational model is reflected in the hardware structure and operating system, and is also the explicit message passing communication seen by the programmer. According to Seitz 985 :It was a premise of the Cosmic Cube experiment that the internode communication should scale well to very large numbers of nodes. A ''direct'' network like the hypercube satisfies this requirement, with respect to both the aggregate bandwidth achieved across the many concurrent communication channels and the feasibility of the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Actor Model And Process Calculi
In computer science, the Actor model and process calculi are two closely related approaches to the modelling of concurrent digital computation. See Actor model and process calculi history. There are many similarities between the two approaches, but also several differences (some philosophical, some technical): *There is only one Actor model (although it has numerous formal systems for design, analysis, verification, modeling, ''etc.''); there are numerous process calculi, developed for reasoning about a variety of different kinds of concurrent systems at various levels of detail (including calculi that incorporate time, stochastic transitions, or constructs specific to application areas such as security analysis). *The Actor model was inspired by the laws of physics and depends on them for its fundamental axioms, ''i.e.'' physical laws (see Actor model theory); the process calculi were originally inspired by algebra . *Processes in the process calculi are anonymous, and commun ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Actor Model Early History
In computer science, the Actor model, first published in 1973, is a mathematical model of concurrent computation. Event orderings versus global state A fundamental challenge in defining the Actor model is that it did not provide for global states so that a computational step could not be defined as going from one global state to the next global state as had been done in all previous models of computation. In 1963 in the field of Artificial Intelligence, John McCarthy introduced situation variables in logic in the Situational Calculus. In McCarthy and Hayes 1969, a situation is defined as "the complete state of the universe at an instant of time." In this respect, the situations of McCarthy are not suitable for use in the Actor model since it has no global states. From the definition of an Actor, it can be seen that numerous events take place: local decisions, creating Actors, sending messages, receiving messages, and designating how to respond to the next message received. Partia ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Denotational Semantics
In computer science, denotational semantics (initially known as mathematical semantics or Scott–Strachey semantics) is an approach of formalizing the meanings of programming languages by constructing mathematical objects (called ''denotations'') that describe the meanings of expressions from the languages. Other approaches providing formal semantics of programming languages include axiomatic semantics and operational semantics. Broadly speaking, denotational semantics is concerned with finding mathematical objects called domains that represent what programs do. For example, programs (or program phrases) might be represented by partial functionsDana S. ScottOutline of a mathematical theory of computation Technical Monograph PRG-2, Oxford University Computing Laboratory, Oxford, England, November 1970.Dana Scott and Christopher Strachey. ''Toward a mathematical semantics for computer languages'' Oxford Programming Research Group Technical Monograph. PRG-6. 1971. or by games ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Petri Net
A Petri net, also known as a place/transition (PT) net, is one of several mathematical modeling languages for the description of distributed systems. It is a class of discrete event dynamic system. A Petri net is a directed bipartite graph that has two types of elements, places and transitions. Place elements are depicted as white circles and transition elements are depicted as rectangles. A place can contain any number of tokens, depicted as black circles. A transition is enabled if all places connected to it as inputs contain at least one token. Some sources state that Petri nets were invented in August 1939 by Carl Adam Petri—at the age of 13—for the purpose of describing chemical processes. Like industry standards such as UML activity diagrams, Business Process Model and Notation, and event-driven process chains, Petri nets offer a graphical notation for stepwise processes that include choice, iteration, and concurrent execution. Unlike these standards, Petri nets hav ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
