Petri nets

In computer science, the Actor model, first published in 1973 (Hewitt et al. 1973), is a mathematical model of concurrent computation. The Actor model treats “Actors” as the universal primitives 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 determine how to respond to the next message received. The Actor model has been used both as a framework within which to develop a theor ...

Including:

• Actor model - History
• Actor model - Fundamental concepts
• Actor model - Formal systems
• Actor model - Applications
• Actor model - Models prior to the Actor model
• Actor model - Lambda calculus
• Actor model - Simula
• Actor model - Smalltalk
• Actor model - Petri nets
• Actor model - Message Passing Semantics
• Actor model - The unbounded nondeterminism controversy
• Actor model - Direct communication and asynchrony
• Actor model - Actor creation plus addresses in messages means variable topology
• Actor model - Inherently concurrent
• Actor model - No requirement on order of message arrival
• Actor model - Not sequentiality not buffering not synchrony and not fixed topology
• Actor model - Locality
• Actor model - Compositionality
• Actor model - Behaviors
• Actor model - Relationship to mathematical logic
• Actor model - Migration
• Actor model - Security
• Actor model - Synthesizing addresses of Actors
• Actor model - Why is the Actor model important now?
• Actor model - Actor researchers

Read more here: » Actor model: Encyclopedia - Actor model

Workflow is the operational aspect of a work procedure: how tasks are structured, who performs them, what their relative order is, how they are synchronized, how information flows to support the tasks and how tasks are being tracked. As the dimension of time is considered in Workflow, Workflow considers "throughput" as a distinct measure. Workflow problems can be modeled and analyzed using Petri nets. While the concept of workflow is not specific to information technology, support for work ...

Including:

• Workflow - Workflow systems

Read more here: » Workflow: Encyclopedia - Workflow

An important part of the concept of place is the sociological implication. Place, for a person, may indicate not only location, but position in society, relative wealth, status, and so forth. Place may also refer to an individual's or family's relative status and relationship as compared to other individuals, groups, or families. Elements that turn space into a place are memories, feelings, social connections and the presenc ...

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Transition. In telecommunication, a transition is the change from one signal state to another signal state. In music a transition is a change from one unit, section, parameter, or element or set of parameters or elements, to another. Transitions may be smooth and connected, or disjointed and contrasting. In television and film a transition is a change from one scene to another. In politics, transition can be

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In the context of hardware and software systems, formal verification is the act of proving or disproving the correctness of a system with respect to a certain formal specification or property, using formal methods. Software testing cannot prove that a system has no defects. Only the process of formal verification can prove that a system has no defects. That said, since the proofs or proof engines themselves are typically complex systems constructed by fallible humans, we are ...

Including:

• Formal verification - Validation and Verification

Read more here: » Formal verification: Encyclopedia - Formal verification

Genes can be viewed as nodes in a complex network, with input being proteins such as transcription factors, and outputs being the level of gene expression. The node itself can also be viewed as a function which can be obtained by combining basic functions upon the inputs (in the Boolean network described below these are Boolean functions or gates computed using the basic AND OR and NOT gates in electronics). These functions have been interpreted as performing a kind information processing within cell which determine cellular behaviour. The b ...

See also:

Gene regulatory network, Gene regulatory network - Overview, Gene regulatory network - Example: Boolean network, Gene regulatory network - Sources, Gene regulatory network - Books, Gene regulatory network - External links

Read more here: » Gene regulatory network: Encyclopedia II - Gene regulatory network - Overview

Workflow diagram systems are defined as "systems that help organizations to specify, execute, monitor, and coordinate the flow of work cases within a distributed office environment". Workflow diagrams rely on the use of standardized graphical notations to describe workflow structures. The Business Process Modeling Notation is an example of this system. The system contains two basic components: first component is the workflow modeling component (sometimes called the specification module or the build time system), w ...

See also:

Workflow, Workflow - Workflow systems

Read more here: » Workflow: Encyclopedia II - Workflow - Workflow systems

A decades-long goal has been to find repeatable, predictable processes or methodologies that improve productivity and quality. Some try to systematize or formalize the seemingly unruly task of writing software. Others apply project management techniques to writing software. Without project management, software projects can easily be delivered late or over budget. With large numbers of software projects not meeting their expectations in terms of functionality, cost, or delivery schedule, effective project management is proving difficult. See ...

See also:

Software development process, Software development process - Processes and meta-processes, Software development process - Process and methodology, Software development process - Process steps, Software development process - Waterfall processes, Software development process - Iterative processes, Software development process - Agile processes, Software development process - Formal methods, Software development process - Specification-driven development, Software development process - Lists

Read more here: » Software development process: Encyclopedia II - Software development process - Process and methodology

To define a process calculus, one starts with a set of names ( or channels) whose purpose is to provide means of communication. In many implementations, channels have rich internal structure to improve efficiency, but this is abstracted away in most theoretic models. In addition to names, one needs a means to form new processes from old: the crucial operators, always present in some form or other, allow: parallel composition of processes specification which channels to use for sending and receiving data sequentialization of interactions hiding of interac ...

See also:

Process calculi, Process calculi - Essential features, Process calculi - Mathematics of processes, Process calculi - Parallel composition, Process calculi - Communication, Process calculi - Sequential composition, Process calculi - Reduction semantics, Process calculi - Hiding, Process calculi - Recursion and replication, Process calculi - Null process, Process calculi - History, Process calculi - Current research, Process calculi - Relationship to other models of concurrency

Read more here: » Process calculi: Encyclopedia II - Process calculi - Mathematics of processes

Concurrent programming languages are programming languages that use language constructs for concurrency. These constructs may involve multi-threading, support for distributed computing, message passing, shared resources (including shared memory) or futures (known also as promises). Today, the most commonly used programming languages that have specific constructs for concurrency are Java and C#. Both of these languages fundamentally use a shared-memory concurrency model, with locking provided by monitors (although message-passin ...

See also:

Concurrent computing, Concurrent computing - Concurrent interaction and communication, Concurrent computing - Coordinating access to resources, Concurrent computing - Concurrent programming languages, Concurrent computing - Models of concurrency

Read more here: » Concurrent computing: Encyclopedia II - Concurrent computing - Concurrent programming languages

Activity diagrams represent the business and operational workflows of a system. In UML 1.x, an Activity diagram is a variation of the UML State diagram where the "states" represent operations, and the transitions represent the activities that happen when the operation is complete. The UML 2.0 Activity diagram, while similar looking to the UML 1.x Activity diagram, now has semantics based on Petri nets. In UML 2.0, the Interaction Ov ...

See also:

Activity diagram, Activity diagram - Description, Activity diagram - Example Partially Valid

Read more here: » Activity diagram: Encyclopedia II - Activity diagram - Description

The Actor model is about the semantics of message passing. Actor model - The unbounded nondeterminism controversy. Arguably, the first concurrent programs were interrupt handlers. During the course of its normal operation, a computer needed to be able to receive information from outside (characters from a keyboard, packets from a network, etc.). So when the information arrived execution of the computer was "interrupted" and special code called an interrupt handler was called to put the information in a b ...

See also:

Actor model, Actor model - History, Actor model - Fundamental concepts, Actor model - Formal systems, Actor model - Applications, Actor model - Models prior to the Actor model, Actor model - Lambda calculus, Actor model - Simula, Actor model - Smalltalk, Actor model - Petri nets, Actor model - Message Passing Semantics, Actor model - The unbounded nondeterminism controversy, Actor model - Direct communication and asynchrony, Actor model - Actor creation plus addresses in messages means variable topology, Actor model - Inherently concurrent, Actor model - No requirement on order of message arrival, Actor model - Not sequentiality not buffering not synchrony and not fixed topology, Actor model - Locality, Actor model - Compositionality, Actor model - Behaviors, Actor model - Relationship to mathematical logic, Actor model - Migration, Actor model - Security, Actor model - Synthesizing addresses of Actors, Actor model - Why is the Actor model important now?, Actor model - Actor researchers

Read more here: » Actor model: Encyclopedia II - Actor model - Message Passing Semantics

Verification is one aspect of testing a product's fitness for purpose. Validation is the complementary aspect. Often one refers to the overall checking process as V & V. Validation: "Are we building the right product?", i.e., does the product do what the user really requires. Verification: "Are we building the product right?", i.e., does the product conform to the specifications. The verification process consists of static and dynamic parts. E.g., for a software product one can inspect the ...

See also:

Formal verification, Formal verification - Validation and Verification

Read more here: » Formal verification: Encyclopedia II - Formal verification - Validation and Verification

One of the major issues in concurrent computing is preventing concurrent processes from interfering with each other. For example, consider the following algorithm for making withdrawals from a checking account represented by the shared resource balance: 1 bool withdraw(int withdrawal) { 2 if( balance > withdrawal ) { 3 balance = balance - withdrawal; 4 return true; 5 } else return false; 6 } Suppose balance=500, and two concurrent processes make the calls withdr ...

See also:

Concurrent computing, Concurrent computing - Concurrent interaction and communication, Concurrent computing - Coordinating access to resources, Concurrent computing - Concurrent programming languages, Concurrent computing - Models of concurrency

Read more here: » Concurrent computing: Encyclopedia II - Concurrent computing - Coordinating access to resources

Over the years, several different formal systems have been developed to permit reasoning about systems in the Actor model. These include: Operational semantics (Greif 1975), (Agha, Mason, Smith, and Talcott 1996) Laws for Actor systems(Baker and Hewitt 1977) Denotational semantics (Clinger 1981) Transition semantics See also:

Actor model, Actor model - History, Actor model - Fundamental concepts, Actor model - Formal systems, Actor model - Applications, Actor model - Models prior to the Actor model, Actor model - Lambda calculus, Actor model - Simula, Actor model - Smalltalk, Actor model - Petri nets, Actor model - Message Passing Semantics, Actor model - The unbounded nondeterminism controversy, Actor model - Direct communication and asynchrony, Actor model - Actor creation plus addresses in messages means variable topology, Actor model - Inherently concurrent, Actor model - No requirement on order of message arrival, Actor model - Not sequentiality not buffering not synchrony and not fixed topology, Actor model - Locality, Actor model - Compositionality, Actor model - Behaviors, Actor model - Relationship to mathematical logic, Actor model - Migration, Actor model - Security, Actor model - Synthesizing addresses of Actors, Actor model - Why is the Actor model important now?, Actor model - Actor researchers

Read more here: » Actor model: Encyclopedia II - Actor model - Formal systems

The Actor model built on previous models of computation. Actor model - Lambda calculus. The lambda calculus of Alonzo Church can be viewed as the earliest message passing programming language. For example the lambda expression below implements a tree data structure when supplied with parameters for a leftSubTree and rightSubTree. When such a tree is given a parameter message "getLeft", it returns leftSubTree and likewise when given th ...

See also:

Actor model, Actor model - History, Actor model - Fundamental concepts, Actor model - Formal systems, Actor model - Applications, Actor model - Models prior to the Actor model, Actor model - Lambda calculus, Actor model - Simula, Actor model - Smalltalk, Actor model - Petri nets, Actor model - Message Passing Semantics, Actor model - The unbounded nondeterminism controversy, Actor model - Direct communication and asynchrony, Actor model - Actor creation plus addresses in messages means variable topology, Actor model - Inherently concurrent, Actor model - No requirement on order of message arrival, Actor model - Not sequentiality not buffering not synchrony and not fixed topology, Actor model - Locality, Actor model - Compositionality, Actor model - Behaviors, Actor model - Relationship to mathematical logic, Actor model - Migration, Actor model - Security, Actor model - Synthesizing addresses of Actors, Actor model - Why is the Actor model important now?, Actor model - Actor researchers

Read more here: » Actor model: Encyclopedia II - Actor model - Models prior to the Actor model

In the first half of the 20th century, various formalisms were proposed to capture the informal concept of a computable function, with μ-recursive functions, Turing Machines and the lambda calculus possibly being the best-known examples today. The surprising fact that they are essentially equivalent, in the sense that they are all encodable into each other, is the content of the Church-Turing thesis. Another shared feature is more rarely commented on: they all are most readily understood as models of sequential computation. Th ...

See also:

Process calculi, Process calculi - Essential features, Process calculi - Mathematics of processes, Process calculi - Parallel composition, Process calculi - Communication, Process calculi - Sequential composition, Process calculi - Reduction semantics, Process calculi - Hiding, Process calculi - Recursion and replication, Process calculi - Null process, Process calculi - History, Process calculi - Current research, Process calculi - Relationship to other models of concurrency

Read more here: » Process calculi: Encyclopedia II - Process calculi - History

The following example illustrates how a Boolean network can model a GRN together with its gene products (the outputs) and the substances from the environment that affect it (the inputs). Stuart Kauffman was amongst the first biologists to use the metaphor of Boolean networks to model genetic regulatory networks. Each gene, each input, and each output is represented by a node in a directed graph in which there is an arrow from one node to another if and only if there is a causal link between the two nodes. Each node in t ...

See also:

Gene regulatory network, Gene regulatory network - Overview, Gene regulatory network - Example: Boolean network, Gene regulatory network - Sources, Gene regulatory network - Books, Gene regulatory network - External links

Read more here: » Gene regulatory network: Encyclopedia II - Gene regulatory network - Example: Boolean network

Some software development methods: Top-Down Model Bottom Up Waterfall model V model Spiral model Chaos model Prototyping Evolutionary prototyping Iterative and Incremental development Extreme Programming Rational Unified Process Some paradigms for programming software: Procedural programming Structured programming Imperative programming Declarative programming Functional program ...

See also:

Software development process, Software development process - Processes and meta-processes, Software development process - Process and methodology, Software development process - Process steps, Software development process - Waterfall processes, Software development process - Iterative processes, Software development process - Agile processes, Software development process - Formal methods, Software development process - Specification-driven development, Software development process - Lists

Read more here: » Software development process: Encyclopedia II - Software development process - Lists

On the 40th anniversary of the publication of Moore's Law, hardware development is furthering both local and nonlocal massive concurrency. Local concurrency is being enabled by new hardware for 64-bit many-core (Platform 2015 Unveiled at IDF Spring 2005) microprocessors, multi-chip modules, and high performance interconnect. Nonlocal concurrency is being enabled by new hardware for wired and wireless broadband packet switched communications (see Wi-Fi and Ultra wideband). ...

See also:

Actor model, Actor model - History, Actor model - Fundamental concepts, Actor model - Formal systems, Actor model - Applications, Actor model - Models prior to the Actor model, Actor model - Lambda calculus, Actor model - Simula, Actor model - Smalltalk, Actor model - Petri nets, Actor model - Message Passing Semantics, Actor model - The unbounded nondeterminism controversy, Actor model - Direct communication and asynchrony, Actor model - Actor creation plus addresses in messages means variable topology, Actor model - Inherently concurrent, Actor model - No requirement on order of message arrival, Actor model - Not sequentiality not buffering not synchrony and not fixed topology, Actor model - Locality, Actor model - Compositionality, Actor model - Behaviors, Actor model - Relationship to mathematical logic, Actor model - Migration, Actor model - Security, Actor model - Synthesizing addresses of Actors, Actor model - Why is the Actor model important now?, Actor model - Actor researchers

Read more here: » Actor model: Encyclopedia II - Actor model - Why is the Actor model important now?