# Actor model and process calculi history

**Milner, et al.**

The Actor model and process calculi share an interesting history and co-evolution.wikipedia

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### Actor model

**actorsactorActor programming**

The Actor model and process calculi share an interesting history and co-evolution.

The original communicating sequential processes (CSP) model published by Tony Hoare differed from the actor model because it was based on the parallel composition of a fixed number of sequential processes connected in a fixed topology, and communicating using synchronous message-passing based on process names (see Actor model and process calculi history).

### Actor model and process calculi

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

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).

See Actor model and process calculi history.

### History of the Actor model

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

### Process calculus

**process calculiprocess algebracalculus**

The Actor model and process calculi share an interesting history and co-evolution.

### Concurrent computing

**concurrentconcurrent programmingconcurrency**

The Actor model, first published in 1973, is a mathematical model of concurrent computation.

### Actor model theory

**Actor event diagramsarrival orderingtheoretical understanding**

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

### Robin Milner

**MilnerArthur John Robin Gorell MilnerA J Milner**

The approach taken in developing the theoretical version of CSP was heavily influenced by Robin Milner's work on the Calculus of Communicating Systems (CCS), and vice versa.

### Communicating sequential processes

**CSPCommunicating Sequential Processes (CSP)channel**

The publication by Tony Hoare in 1978 of the original Communicating Sequential Processes was different from the Actor model which states:

### Consistency

**consistentinconsistentlogically consistent**

### Starvation (computer science)

**starvationresource starvationscheduling starvation**

### Unbounded nondeterminism

**fairnessbounded nondeterminismfair**

Will Clinger [1981] developed the first denotational Actor model for concurrent computation that embodied unbounded nondeterminism.

### Stephen Brookes

Tony Hoare, Stephen Brookes, and A. W. Roscoe developed and refined the theory of CSP into its modern form.

### Bill Roscoe

**A. W. RoscoeRoscoe, A.W.**

Tony Hoare, Stephen Brookes, and A. W. Roscoe developed and refined the theory of CSP into its modern form.

### Calculus of communicating systems

**CCSCCS-Calculus**

The approach taken in developing the theoretical version of CSP was heavily influenced by Robin Milner's work on the Calculus of Communicating Systems (CCS), and vice versa. His work on representing Actor abstraction and composition, and on developing an operational semantics for Actors based on asynchronous communications trees was explicitly influenced by Milner's work on the Calculus of Communicating Systems (CCS).

### Gul Agha (computer scientist)

**Gul AghaAgha**

Agha developed Actors as a fundamental model for concurrent computation.

### Operational semantics

**operationalnatural semanticsOperationally**

His work on representing Actor abstraction and composition, and on developing an operational semantics for Actors based on asynchronous communications trees was explicitly influenced by Milner's work on the Calculus of Communicating Systems (CCS).

### Π-calculus

**pi-calculusPi calculus-calculus**

Milner later removed some of these restrictions in his work on the Pi calculus (see section Milner, et al. below).

### Communication channel

**channelchannelscommunications channel**

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).

### Denotational semantics

**denotationalfully abstractHistory of denotational semantics**

### Prentice Hall

**Prentice-HallPearson Prentice HallPrentice Hall Press**

### Tony Hoare

**C. A. R. HoareC.A.R. HoareHoare**

Tony Hoare, Stephen Brookes, and A. W. Roscoe developed and refined the theory of CSP into its modern form.