Peter W. Madany

An overview of the Spring system

Spring is a highly modular, distributed, object-oriented operating system. This paper describes the goals of the Spring system and provides overviews of the Spring object model, the security model, and the naming architecture. Implementation details of the Spring microkernel, virtual memory system, file system, and UNIX emulation are supplied.<<ETX>>

Designing and implementing Choices : an object-oriented system in C++

We describe our experiences in constructing Choices and a design methodology that extends existing design approaches by explicitly encouraging specialization, as well as design and code reuse. Although many operating system techniques and designs are well documented, few object-oriented operating systems exist and have been described. SOS [23], CHORUS [18], and Apertos [26] are other examples of object-oriented operating systems. None of the descriptions of the design of these operating systems provide a methodology for design reuse or describe how the design methodology may be used in conjunction with prototyping

Choices, frameworks and refinement

Presents a method for designing operating systems using object-oriented frameworks. A framework can be refined into subframeworks. Constraints specify the interactions between the subframeworks. The authors describe how they used object-oriented frameworks to design Choices, an object-oriented operating system.<<ETX>>

Organizing and typing persistent objects within an object-oriented framework

Conventional operating systems provide little or no direct support for an efficient persistent object system implementation. The authors have built a persistent object scheme using a customization and extension of an object-oriented operating system called Choices. Both conventional file systems and persistent object systems are constructed within the same framework for the storage of persistent data. The persistent object store supports a wide range of persistent object sizes, extensible sets of persistent object types and automated garbage collection and associates each object with its class and operations. To improve performance, collections of persistent object can be accessed as an aggregate. Light-weight persistent objects may be clustered within persistent object containers. In this paper the authors describe how persistent objects are named and used within Choices, and three areas in which persistent object support differs from file system support: storage organization, storage management, and typing.<<ETX>>

Persistence in the Spring system

The Spring system does not provide persistent object identifiers and not all Spring objects are persistent. Instead, we rely on a general name service and persistent name-to-object bindings to support persistence. The name service is separate from the various subsystems that implement persistent objects, so that new object types can be added, and the implementation of existing types can be changed, without rebuilding the name service. We distinguish among the concepts of freezing, pickling, and externalizing. We then develop a general framework for freezing that can be used by any client, including the name server,for making objects persistent. It allows subsystems that implement objects of various types to maintain autonomy from the name service and retain control over how their objects are implemented and made persistent, and yet be well integrated with the name service.<<ETX>>

Considerations of Persistence and Security in Choices, an Object-Oriented Operating System

Choices is an object-oriented operating system written in an object-oriented language and runs on bare hardware. It supports distributed, parallel applications on a network of multiprocessors. The kernel is implemented as a dynamic collection of objects that have been instantiated from classes. The classes are represented as objects at run-time. Choices has a paged virtual memory organized around memory objects. Each memory object can have its own separate backing store, page placement, and page replacement algorithms. It can be shared, both within a shared memory multiprocessor and between networked computers using a distributed virtual memory protocol.

The design of an object-oriented operating system (abstract): a case study of choices

The Design of an Object-Oriented Operating System: A Case Studyof ChoicesRoy H. Campbell & Nayeem Islam, University of IllinoisPeter W. Madany, SUN Microsystems This tutorial describes the object-oriented design of a completeoperating system, written to be object-oriented, with a user andapplication interface that is object-oriented. The main objectiveis to illustrate object-oriented design trade-offs by studying alarge object-oriented system, the Choices operating system. Choices is an object-oriented multiprocessor operating systemthat runs native on SPARC stations, Encore Multimaxes, and IBM PCs.The system is built from a number of frameworks that implement ageneral file system, persistent store for persistent objects,process switching, parallel processing, distributed processing,interrupt handling, virtual memory, networking, and interprocesscommunication. If you bring an IBM/PC 386-based portable computer runningMS-DOS to the course then you may experiment by writing applicationprograms for PC-Choices. All participants will receive a copy ofPC-Choices on a floppy. Participants should have experience with buildingobject-oriented systems and have a basic understanding of operatingsystems design. Reading knowledge of C++ is helpful, but notnecessary.