Dependable distributed systems are difficult to build. This is particularly true if they have
dependability requirements that change during the execution of an application, and are built
with commercial off-the-shelf hardware. In that case, fault tolerance must be achieved using
middleware software, and mechanisms must be provided to communicate the dependability
requirements of a distributed application to the system and to adapt the system's
configuration to try to achieve the desired dependability. The AQuA architecture allows …

Building dependable distributed systems from commercial off-the-shelf components is of
growing practical importance. For both cost and production reasons, there is interest in
approaches and architectures that facilitate building such systems. The AQuA architecture is
one such approach; its goal is to provide adaptive fault tolerance to CORBA applications by
replicating objects. The AQuA architecture allows application programmers to request
desired levels of dependability during applications' runtimes. It provides fault tolerance …