Embedded operating system (OS) kernels provide basic execution primitives that can be used commonly by many appliances. The recent emergence of digital appliances requires more advanced features, such as networking and GUI. Those features dramatically complicate the appliances' software systems and increase their code sizes. In order to develop such large and complex software systems, we propose a system architecture that co-locates multiple embedded operating systems on a microkernel. The proposed architecture employs a microkernel to provide protected execution environments for the existing embedded kernels. In each protected execution environment, a kernel and its applications run just as they run directly on hardware since they share the same protection domain. Our approach can achieve the maximum reusability of the existing software resources including embedded OS kernels and their applications; thus, it protects the existing software resources. We have developed the system that consists of TL4 microkernel and a /spl mu/ITRON embedded kernel, and shows the feasibility of our approach through evaluations.

EarlGray is a component-based Java virtual machine (JVM) that can be configured to satisfy various kinds of requirements for building future information appliances and embedded systems. While the modification and extension on an existing JVM tend to be done in an ad-hoc manner, EarlGray allows developers to customize the JVM in a systematic manner by decomposing it into components and the explicit descriptions of the relationship between the components. We also examine three case studies on the customization of the EarlGray: exchanging a scheduler, memory management, and class file verifier components. These case studies show the benefits and drawbacks of the current component-based technologies.

Embedded computers pervade our lives. There are increasing opportunities for them to adopt embedded operating systems as they are required to have high functionality and complexity. Unfortunately, the reliability of such embedded systems is insufficient to support our lives in 24/7. Therefore, we propose the fine-grain proactive recovery (FPR) of operating system components. FPR enables an operating system to periodically restart its modules and thus to keep their states clean.

The number of various kinds of everyday objects that contain embedded computers is increasing due to the popularity of ubiquitous computing. While component-based software development becomes common in a variety of application domains, ubiquitous computing requires component frameworks that offer more advanced features than the current component frameworks. This paper explores a component framework in the context of a ubiquitous computing system. We design and implement a system coordinating various home appliances, called SENCHA. SENCHA is built on the OSGi component framework. Although the framework provides facilities for dynamically changing environments, this paper reveals several problems of the framework in our experience

Our daily lives will be dramatically changed by embedded small computers in our environments. The environments are called ubiquitous computing environments. To realize the environments, it is important to reduce the cost to develop ubiquitous computing applications by encapsulating complex issues in middleware infrastructures that are shared by various applications.In this paper, we describe three middleware infrastructures for supporting ubiquitous computing, that have developed in our projects. Our infrastructures have tried to hide some complexities to make it easy to develop ubiquitous computing applications in an easy way. We also show some lessons learned in our projects.