# Actor model theory

**Actor event diagramsarrival orderingtheoretical understanding**

In theoretical computer science, Actor model theory concerns theoretical issues for the Actor model.wikipedia

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### Actor model

**actorsactorActor programming**

In theoretical computer science, Actor model theory concerns theoretical issues for the Actor model.

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.

### Denotational semantics of the Actor model

**Clinger's modeldenotational modelsdenotational semantics**

Actor model theory incorporates theories of the events and structures of Actor computations, their proof theory, and denotational models.

### Indeterminacy in concurrent computation

**indeterminacydeterminacydeterminism**

The arrival ordering means that the Actor model inherently has indeterminacy (see Indeterminacy in concurrent computation).

Hewitt [1985] and Agha [1991], and other published work argued that mathematical models of concurrency did not determine particular concurrent computations as follows: The Actor model makes use of arbitration (often in the form of notional arbiters) for determining which message is next in the arrival ordering of an Actor that is sent multiple messages concurrently.

### History of the Actor model

**Actor model early historyEvent orderings versus global statethe actor model**

Partial orderings on such events have been axiomatized in the Actor model and their relationship to physics explored (see Actor model theory).

### Actor model and process calculi

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

### Actor model implementation

**Cosmic Cubepractical implementations**

### Theoretical computer science

**theoretical computer scientisttheoreticalcomputer science**

In theoretical computer science, Actor model theory concerns theoretical issues for the Actor model.

### General relativity

**general theory of relativitygeneral relativity theoryrelativity**

### Invariant (physics)

**invariantinvarianceInvariance (physics)**

### Frame of reference

**reference frameframes of referencereference frames**

### Arbiter (electronics)

**arbiterarbitersarbitration**

Arrival ordering is determined by arbitration in processing messages (often making use of a digital circuit called an arbiter).

### World line

**worldlineworld linesworld-line**

The arrival events of an Actor are on its world line.

### Zeno machine

The law of discreteness rules out Zeno machines and is related to results on Petri nets [Best et al. 1984, 1987].

### Petri net

**Petri netsPetri net theoryconcurrent systems**

The law of discreteness rules out Zeno machines and is related to results on Petri nets [Best et al. 1984, 1987].

### Unbounded nondeterminism

**fairnessbounded nondeterminismfair**

The Law of Discreteness implies the property of unbounded nondeterminism.

### Denotational semantics

**denotationalfully abstractHistory of denotational semantics**

The combined ordering is used by [Clinger 1981] in the construction of a denotational model of Actors (see denotational semantics).

### Actor model and process calculi history

**Milner, et al.**

In the Actor model sequentiality was a special case that derived from concurrent computation as explained in Actor model theory.

### Parallel computing

**parallelparallel processingparallelism**

Logics such as Lamport's TLA+, and mathematical models such as traces and Actor event diagrams, have also been developed to describe the behavior of concurrent systems.

### Power domains

**Powerdomain**

Clinger [1981] constructed a power domain for the Actor model building on the base domain of Actor event diagrams, which is incomplete.