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Quality of Service in Object Oriented Systems

Attila Ulbert
( Hungarian )

Eötvös Lorand University
Fehervary str. 235 V/17 H-1116 Budapest
tel:
fax:
mormota@elte.hu

Keywords:

distribution frameworks meta architectures multimedia applications distributed object computing middleware remote invocations adaptive programming

Abstract:

Most object-oriented framework for distributed programming doesn't enable the developer to adapt his application to the constantly changing environment. They offer just a fixed set of invocation semantics, which is inherently not extensible by the user. This kind of brittleness of such systems makes their evolution relatively slow. Before the users can make benefit of the new results techniques in wired/wireless communication, the framework has to be extended or even modified by its developers.

A few years ago the OMG was of the opinion that ,,CORBA, as it exists today, is perfectly suited for wireless access''. The early CORBA specifications deemed the presumption of reliable transport less restrictive, but with the emergence of wireless networks it turned out to be one of the major problems of CORBA in mobile environments. An other field occupying the CORBA researchers is the multimedia communication and Quality of Service (QoS).

In my research I try to such an answer to the new challenges, that allows the application developer to apply high level abstractions (like method invocation) and enables him to extend the framework with arbitrary new interaction modes. The ORB(M) system implements my answers. The ORB(M) framework represents the mode of interaction by an extensible class library and offers flexibility via its pluggable semantic elements.

I implemented the prototype ORB(M) framework in C++ environment. The system already includes a fairly large library of semantic elements, implementing synchronous, asynchronous and oneway invocation, TCP and UDP based oneway and twoway communication. The library can easily be supplemented, enabling the user to create arbitrary new semantics by combining the semantic elements in the library. Moreover, the semantics are attached to the methods and not the objects, thus each method can have its own invocation features.

The performance measurements show, that the ORB(M) framework is faster than one of the fastest CORBA implementation, even with its default interaction mode (synhronous remote invocation). The adaptation of semantic elements to the specialities of the task results about 20-50% shorter delays. I admit, that the short delays are partly resulted by the fact, that the framework is not a full-featured CORBA implementation, however the numbers proved that the concept of pluggable semantic elements can effectively be applied in distributed object communication.

The PhD work started: Sept. 1999

The submitted work will probably not be presented in the
upcoming ECOOP PhD Workshop.

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Last modified on Mon Aug 15 14:59:24 2005