With Reactive Systems becoming the new old hotness, it will help to have a thorough grounding in the Actor Model. Here's a good start. Carl Hewitt in Actor Model of Computation: Scalable Robust Information Systems gives a very thorough and relatively concise explanation of the Actor model.

Here's the abstract.

The Actor model is a mathematical theory that treats "Actors" as the universal primitives of concurrent digital computation. The model has been used both as a framework for a theoretical understanding of concurrency, and as the theoretical basis for several practical implementations of concurrent systems. Unlike previous models of computation, the Actor model was inspired by physical laws. It was also influenced by the programming languages Lisp, Simula 67 and Smalltalk-72, as well as ideas for Petri Nets, capability-based systems and packet switching. The advent of massive concurrency through client-cloud computing and many-core computer architectures has galvanized interest in the Actor model.



Actor technology will see significant application for integrating all kinds of digital information for individuals, groups, and organizations so their information usefully links together. Information integration needs to make use of the following information system principles:

* Persistence. Information is collected and indexed.

* Concurrency: Work proceeds interactively and concurrently, overlapping in time.

* Quasi-commutativity: Information can be used regardless of whether it initiates new work or become relevant to ongoing work.

* Sponsorship: Sponsors provide resources for computation, i.e., processing, storage, and communications.

* Pluralism: Information is heterogeneous, overlapping and often inconsistent.

* Provenance: The provenance of information is carefully tracked and recorded

The Actor Model is intended to provide a foundation for inconsistency robust information integration.