# Actor model and process calculi

**issues with getting messages from multiple channelsmigrationSynchronous channels in process calculiunbounded channels**

In computer science, the Actor model and process calculi are two closely related approaches to the modelling of concurrent digital computation.wikipedia

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### Actor model

**actorsactorActor programming**

In computer science, the Actor model and process calculi are two closely related approaches to the modelling of concurrent digital computation. Will Clinger (building on the work of Irene Greif [1975], Gordon Plotkin [1976], Henry Baker [1978], Michael Smyth [1978], and Francez, Hoare, Lehmann, and de Roever [1979]) published the first satisfactory mathematical denotational theory of the Actor model using domain theory in his dissertation in 1981. His semantics contrasted the unbounded nondeterminism of the Actor model with the bounded nondeterminism of CSP [Hoare 1978] and Concurrent Processes [Milne and Milner 1979] (see denotational semantics).

The relationship of the model to other work is discussed in Actor model and process calculi.

### Communication channel

**channelchannelscommunications channel**

### Actor model and process calculi history

**Milner, et al.**

See Actor model and process calculi history.

However, the goal of Milner and Hoare to attain an algebraic calculus led to a critical divergence from the Actor model: communication in the process calculi is not direct as in the Actor model but rather indirectly through channels (see Actor model and process calculi).

### Process calculus

**process calculiprocess algebracalculus**

In computer science, the Actor model and process calculi are two closely related approaches to the modelling of concurrent digital computation.

The use of channels for communication is one of the features distinguishing the process calculi from other models of concurrency, such as Petri nets and the actor model (see Actor model and process calculi).

### Actor model theory

**Actor event diagramsarrival orderingtheoretical understanding**

### Computer science

**computer scientistcomputer sciencescomputer scientists**

In computer science, the Actor model and process calculi are two closely related approaches to the modelling of concurrent digital computation.

### Concurrency (computer science)

**concurrencyconcurrentconcurrently**

In computer science, the Actor model and process calculi are two closely related approaches to the modelling of concurrent digital computation.

### Scientific law

**laws of physicsphysical lawlaws of nature**

### Algebra

**algebraicAlgebra IAlgebra 1**

### Ambient calculus

**Ambient (computation)ambientsmobile ambients**

### FIFO (computing and electronics)

**FIFOfirst in, first outFIFOs**

### Communicating sequential processes

**CSPCommunicating Sequential Processes (CSP)channel**

However, simple synchronous channels do not suffice for process calculi such as Communicating Sequential Processes (CSP) [Hoare 1978 and 1985] because use of the guarded choice (after Dijkstra) command (called the alternative command in CSP). His semantics contrasted the unbounded nondeterminism of the Actor model with the bounded nondeterminism of CSP [Hoare 1978] and Concurrent Processes [Milne and Milner 1979] (see denotational semantics).

### Two-phase commit protocol

**two-phase committwo phase commit2-phase commit**

Because only one guard can be chosen, a guarded choice command in general effectively requires a kind of two-phase commit protocol or perhaps even a three-phase commit protocol if time-outs are allowed in guards (as in Occam 3 [1992]).

### Three-phase commit protocol

Because only one guard can be chosen, a guarded choice command in general effectively requires a kind of two-phase commit protocol or perhaps even a three-phase commit protocol if time-outs are allowed in guards (as in Occam 3 [1992]).

### Timeout (computing)

**timeouttimeoutstime-out**

Because only one guard can be chosen, a guarded choice command in general effectively requires a kind of two-phase commit protocol or perhaps even a three-phase commit protocol if time-outs are allowed in guards (as in Occam 3 [1992]).

### Starvation (computer science)

**starvationresource starvationscheduling starvation**

As pointed out in Knabe [1992], a problem with the above protocol (A simple distributed protocol) is that the process might never accept the message from (a phenomenon called starvation) and consequently the above program might never print anything.

### Deadlock

**livelockdeadlocksdeadly embrace**

As pointed out in Knabe [1992], an issue with the above protocol (A simple distributed protocol) is that the process might never accept a bid from or (a phenomenon called livelock) and consequently might never be sent anything.

### Π-calculus

**pi-calculusPi calculus-calculus**

Agha's Aπ Actor calculus is based on a typed version of the asynchronous π-calculus.

### Irene Greif

Will Clinger (building on the work of Irene Greif [1975], Gordon Plotkin [1976], Henry Baker [1978], Michael Smyth [1978], and Francez, Hoare, Lehmann, and de Roever [1979]) published the first satisfactory mathematical denotational theory of the Actor model using domain theory in his dissertation in 1981.

### Henry Baker (computer scientist)

**Henry BakerBaker**

Will Clinger (building on the work of Irene Greif [1975], Gordon Plotkin [1976], Henry Baker [1978], Michael Smyth [1978], and Francez, Hoare, Lehmann, and de Roever [1979]) published the first satisfactory mathematical denotational theory of the Actor model using domain theory in his dissertation in 1981.

### Denotational semantics

**denotationalfully abstractHistory of denotational semantics**

Will Clinger (building on the work of Irene Greif [1975], Gordon Plotkin [1976], Henry Baker [1978], Michael Smyth [1978], and Francez, Hoare, Lehmann, and de Roever [1979]) published the first satisfactory mathematical denotational theory of the Actor model using domain theory in his dissertation in 1981. His semantics contrasted the unbounded nondeterminism of the Actor model with the bounded nondeterminism of CSP [Hoare 1978] and Concurrent Processes [Milne and Milner 1979] (see denotational semantics).

### Domain theory

**domainsdomaindomain theoretic**

Will Clinger (building on the work of Irene Greif [1975], Gordon Plotkin [1976], Henry Baker [1978], Michael Smyth [1978], and Francez, Hoare, Lehmann, and de Roever [1979]) published the first satisfactory mathematical denotational theory of the Actor model using domain theory in his dissertation in 1981.

### Denotational semantics of the Actor model

**Clinger's modeldenotational modelsdenotational semantics**

### Unbounded nondeterminism

**fairnessbounded nondeterminismfair**

His semantics contrasted the unbounded nondeterminism of the Actor model with the bounded nondeterminism of CSP [Hoare 1978] and Concurrent Processes [Milne and Milner 1979] (see denotational semantics).