Jürg Gutknecht
ETH Zürich

Active Object System (AOS)

Active objects in our terminology are objects together with an integrated
thread of control. Based on the metaphor of active objects and on the Oberon
programming language we have implemented an extremely compact light-weight
kernel called AOS, running on Intel SMP (symmetric multiprocessor)
platforms. The runtime model used is a dynamic population of communicating
and collaborating "agents" (active objects). They come in a great variety of
forms and granularities comprising, for example, device drivers, network
controllers, interaction commanders, and remote terminals (Telnet and VNC).
Active components can easily be plugged-in and plugged-out, which makes AOS
ideally suitable to support a wide spectrum of applications including
servers and "wearable devices". Worth to be mentioned from the
implementation perspective are system-managed conditions (replacing the
traditional signals and contributing to the scalability of the system) and a
carefully thought-through modular ordering that statically guarantees
absence of deadlocks up to a very high degree.