In the actor programming model, the program is run by a set of concurrently executing entities called actors. Actor systems resemble human organizations, such as companies, governments, or other large institutions. To understand this similarity, we consider the example of a large software company.

In a software company like Google, Microsoft, Amazon, or Typesafe, there are many goals that need to be achieved concurrently. Hundreds or thousands of employees work towards achieving these goals, and are usually organized in a hierarchical structure. Different employees work at different positions. A team leader makes important technical decisions for a specific project, a software engineer implements and maintains various parts of a software product, and a system administrator makes sure that the personal workstations, servers, and various equipments are functioning correctly. Many employees, such as the team leader, delegate their own tasks to other employees who are lower...