AspectIX contributions to the ECOOP’98 conference

Unlike CORBA with its static client-server relationship, AspectIX uses the concept of distributed objects. Distributed objects consist of so called fragments, that communicate with other fragments to synthesize the desired behaviour. The local fragment can carry more semantics than a simple CORBA stub and can be replaced at runtime by another fragment to fulfill the application’s requirements. AspectIX therefore provides a single mechanism that is especially suited to realize both: mobility and replication. 1 The AspectIX Architecture From the outside, an AspectIX implementation looks like a standard CORBA implementation [3]. There are location transparent names for objects, which are converted to a local object referring to the distributed object. Unlike CORBA, the AspectIX architecture adopts a fragmented object model similar to Fragmented Objects from INRIA [2] and Globe from the Vrije Universiteit Amsterdam [4]. A distributed object consists of several so called fragments, which can interact with each other. A client of the object needs at least one of these fragments in its local address space. A fragment could be a simple stub (as in CORBA), which is created on the client side and connects to another server-fragment. On the other hand, fragments at the client side can be more intelligent, e.g. by realizing real-time constraints on the communication channel or replication strategies. The local fragment of a distributed object provides an interface described in CORBA IDL. When a fragment is created, e.g. as a result parameter of a method invocation, the ORB creates two local objects in the desired target language: a fragment interface and a fragment implementation. The fragment interface is a generic object that is automatically generated during the development process. It only depends on the IDL description of the distributed object’s interface and its main purpose is to delegate method calls to the fragment implementation. In the simplest case, the implementation does nothing more than a remote method invocation, thus the combination of interface and implementation object realizes the same semantics as a traditional CORBA stub.