Emerald is an object-based language and system designed for the construction of distributed programs. An explicit goal of Emerald is support for object mobility; objects in Emerald can freely move within the system to take advantage of distribution and dynamically changing environments. We say that Emerald has fine-grained mobility because Emerald objects can be small data objects as well as process objects. Fine-grained mobility allows us to apply mobility in new ways but presents imple-mentation problems as well. This paper discusses the benefits of tine-grained mobility, the Emerald language and run-time mechanisms that support mobility, and techniques for implementing mobility that do not degrade the performance of local operations. Performance measurements of the current implementation are included.

ion : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 30 3.1.3 Inheritance and Subclassing : : : : : : : : : : : : : : : : : : : : : : : : : : 32 3.1.4 Polymorphism : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 33 3.2 Definitions : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 36 3.2.1 Object-Oriented Language : : : : : : : : : : : : : : : : : : : : : : : : : : : 36 3.2.2 Object-Oriented System : : : : : : : : : : : : : : : : : : : : : : : : : : : : 37 3.3 Summary : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 38 4 Object-Oriented Operating Systems : : : : : : : : : : : : : : : : : : : : : : : : 40 4.1 Definition of an Object-Oriented Operating System : : : : : : : : : : : : : : : : : 40 4.2 Advantages of Object-Oriented Operating Systems : : : : : : : : : : : : : : : : : 43 4.2.1 Portability Advantages : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 43 4.2.2 Code Sharing Adv...

this paper. The rest of this paper is organized as follows. An overview of the Clouds project is provided in section 2, followed by an overview of the Clouds paradigm in section 3. The paradigm is the common link between the first implementation of Clouds (Clouds v.1) and the current version (Clouds v.2).

This paper addresses the issues faced when constructing an operating system and its kernel with object-oriented technology. We first propose object/metaobject separation, a means of constructing an object-oriented operating system and its kernel. This method divides the implementing system facilities and applications into two types: objects and metaobjects. This paper presents the concept of object/metaobject separation and discusses why object/metaobject separation is required in terms of limitations in the micro-kernel and object-oriented technologies. We also discuss an example of using object/metaobject separation as implemented in Apertos. This paper then proposes mechanisms which efficiently implement object/metaobject separation. These are characterized by meta-level context management, and are implemented in the Apertos operating system. Meta-level context management is designed to reduce the overhead of control transfer between an object and its metaspace. Here, metaobjects re...

This paper presents reflective object management as s set of facilities for handling objects with various properties such as grain-size and lifespan efficiently and naturally. The facilities are classes, variablelength identifiers, memory management, and efficient communication between objects. A class hides details of the implementation of an object such as language and hardware dependency. An identifier is a variable whose length depends on its naming context. There are two or more naming contexts in the system which compose a hierarchical structure. Each naming context guarantees the uniqueness of identifiers it contains. Address spaces are divided into equal sized fragments or slots, and several objects may reside in one address space. This reduces the context switching overhead caused by communication. By tracing communication paths, execution of extra paths can be avoided by replacing them with local procedure calls. These facilities are based on the Muse object architecture and ...

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This paper gives a survey of all common transparent distributed systems. We distinguish between Distributed File Systems (DFS) and Distributed Operating Systems (DOS). Our overview is focussed on systems providing at least access or location transparency. The paper is organized as follows: The introduction offers definitions of the features of each transparent distributed system as well as the services it is able to provide. We also propose a catalog of criteria that enables us to compare different systems independently of implementation done. The main entries we make are heterogeneity of the system's environment, communication strategy, as well as naming and security issues. Finally, we examine the reliability and availability of the separate systems and the way these issues are achieved. The following section consists of the survey. The description of each system is organized as follows: First, we introduce the main goal the system was developed for, the classification of th...