Today, Windows/spl reg/-based (and UNIX/spl reg/-based) PCs have ability to access to the networks at anytime and anyplace. The benefit of such an "always-connected" environment is expanded to non-PC users with new consumer products such as Airboard and CoCoon, which we call the network electronics (or NE) products in this paper.

Flexibility to adapt to different applications is a key requirement of modern operating systems. We have explored the use of meta-objects and reflection as a means to write adaptable system software. The paper discusses the Apertos operating system, that uses these techniques. It outlines how meta-objects help to support flexibility and how we have implemented the concepts, and gives some performance figures.

This paper proposes a methodology for making low-level system code of operating systems be replaceable at runtime. Our approach is to use concurrent objects as a basic programming unit for low-level system programs. To realize the different need for each type of system code and to execute these concurrent objects sufficiently efficient, we use a combination of dedicated system service layers and other implementation techniques. System service layers provide the most suitable primitive operations for each concurrent object. Under our programming model for low-level system code, which we call SCONE, it is possible to program low-level system code without hazardous operations such as explicit synchronization, direct scheduler manipulation, etc. We present the implementation of our methodology on the Apertos operating system and demonstrate its efficiency with performance evaluation.

The hierarchical naming scheme, a method for naming and addressing shared objects in large-scale distributed computer systems, is described. The scheme constructs global identifications (IDs) and addresses from locally unique ones. The IDs have relative representations that are translated if they are transmitted among naming contexts. This ensures uniqueness of IDs while preserving efficiency and availability. Methods that make the scheme suitable for mobile naming contexts and dynamic reconfiguration of networks and systems are reviewed. Implementation issues and solutions are presented.>

This paper proposes a framework for constructing an operating system in an open and mobile computing environment.The framework provides object/metaobject separation and metahierarchy.In the framework, we view object migration as a basic mechanism to accommodate object heterogeneity.The relevance of the proposed framework to existing system structures is discussed.We then present a practical implementation of the Apertos operating system in this framework, where reflectors are introduced for metaobject programming and MetaCore for providing common primitives.We present some evaluation results of the Apertos operating system.We also present related work in terms of reflection mechanisms and systems.

The continued expansion of computer networks and the miniaturization of computers increase the desire to use one's computer in a consistent computational environment, regardless of location and time.In this situation, host migration transparency is very important.This paper introduces a new network architecture which provides host migration transparency in large interconnected networks and proposes a protocol based on the propagating cache method.We introduce the concept virtual network and divide the conventional network layer into two sublayers to realize host migration transparency.Virtual Internet Protocol, or VIP for short, is derived from DARPA-IP as an example of the architecture.We estimate the overhead of VIP.Host migration transparency can be realized without significant processing and traffic overhead.This architecture also preserves host migration transparency across virtual circuits in radio networks.

ConcurrentSmalltalk is an object-oriented concurrent programming language/system which has been running since late 1985. ConcurrentSmalltalk has the following features:

ConcurrentSmalltalk is a programming language/system which incorporates the facilities of concurrent programming in Smalltalk-801. Such facilities are realized by providing concurrent constructs and atomic objects. This paper first gives an outline of ConcurrentSmalltalk. Then, the design of ConcurrentSmalltalk is described. The implementation of ConcurrentSmalltalk is presented in detail.