3rd International Conference on COTS-Based Software Systems

3rd International Conference on COTS-Based Software Systems

A Practical Application of the Ceiling Protocol in a Real-Time System 

This paper briefly discusses some of the real-time design issues that arise when using the priority ceiling protocol for real-time systems. The paper shows a small real-time system design and shows how the code in the system could be structured to satisfy the requirements of the ceiling protocol. This paper will be presented at the 2nd International Workshop on Real-Time Ada Issues in May 1988.

ADA Performance Benchmarks on the Motorola MC68020: Summary and Results

This report documents the results obtained from running Ada performance benchmarks on a DEC VAXELN MicroVAX II using the DEC VAXELN Ada compiler.

ADA Validation Tests for Rate Monotonic Scheduling Algorithm

This report presents a set of tests for checking whether an ADA runtime system properly supports certain rate monotonic scheduling algorithms, specifically, the basic inheritance and priority ceiling protocols.

ADA for Embedded Systems: Issues and Questions

This report addresses issues and questions related to the use of ADA for embedded systems applications; it contains some preliminary recommendations for compilation system implementors, application developers, program managers, and ADA policy makers. The issues and questions provide the context for the Real-Time Embedded Systems Testbed (REST) Project at the SEI, where staff members are investigating software development and performance issues for real-time embedded systems.

ASSIP Study of Real-Time Safety-Critical Embedded Software-Intensive System Engineering Practices

ASSIP Study of Real-Time Safety-Critical Embedded Software-Intensive System Engineering Practices

Analysis of Input/Output Paradigms for Real-Time Systems, An

This paper illustrates how these principles can be applied to input/output interfaces  to predict the timing behavior of various design alternatives.

Analyzing the Reuse Potential of Migrating Legacy Components to a Service-Oriented Architecture

Analyzing the Reuse Potential of Migrating Legacy Components to a Service-Oriented Architecture

Annual Technical Report for ADA Embedded Systems Testbed Project

This technical report provides an overview of the results produced in the first year of the ADA Embedded Systems Testbed Project (through September 30, 1987).

Application-Level Implementation of the Sporadic Server, An

The purpose of this paper is to introduce a sporadic server algorithm that can be implemented as an application-level task, and that can be used when no runtime or operating system level implementation of the sporadic server is available.

Architecture-Centric Approach to Predicting Real-Time Performance

The information sheet describes the SEI architecture-centric toolkit for prediciting end-to-end latency and other qualities of real-time systems.

Architecture-Centric Approach to Predicting Security

This information sheet describes an approach to security analysis that allows software validation by identifying data elements to be protected, components that should be allowed access to those elements, and appropriate communication channels.

Architecture-Centric Approach to Predicting System Reliability

This information sheet describes the SEI architecture-centric, model-based toolkit for more accurate prediction of system reliability.

Architecture-Centric Approach to Predicting System Resource Consumption

This information sheet describes the SEI architecture-centric, model-based toolkit for predicting behavior in bandwidth usage, CPU time, and power consumption.

Assessment of CORBA and POSIX Designs for FAA En Route Resectorization

Modernizing the En Route system presents major acquisition issues to the Federal Aviation Administration (FAA). At the present time, efforts are underway to upgrade the En Route system, primarily focusing on the host computer system. This report addresses the use of different technologies and an architectural tradeoff approach on a typical En Route system problem. We were requested to consider the problem of resectorization, i.e., the combination and decombination of sectors (and fix posting areas) during operation of the En Route center. Such capabilities may become desirable for an implementation of free flight. Two technologies have been applied to develop solutions to this problem, namely Common Object Request Broker Architecture (CORBA) and POSIX.21 (Portable Operating System Interface Standard). The former is based on an object-oriented model, while the latter is based on a message-passing model.

Assurance for Software-Intensive Systems

Assurance for Software-Intensive Systems

Building Secure Systems Using Model-Based Engineering and Architectural Models

Building Secure Systems Using Model-Based Engineering and Architectural Models

Comparative Evaluations of Four Specification Methods for Real-Time Systems

The primary audience of this report is the software development practitioner involved in the method selection or adoption process. The paper attempts to provide proper context to assist the practitioner in making appropriate method adoption decisions. Secondarily, the results of the paper also should be of to tool vendors, method developers, and program managers.

Conceptual Framework for System Fault Tolerance, A

A major problem in transitioning fault tolerance practices to the practitioner community is a lack of a common view of what fault tolerance is, and how it can help in the design of reliable computer systems. This document takes a step towards making fault tolerance more understandable by proposing a conceptual framework. The framework provides a consistent vocabulary for fault tolerance concepts, discusses how systems fail, describes commonly used mechanisms for making systems fault tolerant, and provides some rules for developing fault tolerant systems.

Criteria for Constructing and Using an ADA Embedded System Testbed

The purpose of this report is to list some of the criteria used in five aspects of the project: the hardware configuration, the software configuration, the real-time application, the ADA real-time experiments, and the benchmarking and instrumentation techniques. Each criterion will include a rationale. Each of the criteria listed in this report will be categorized as either essential, highly desirable, or desirable.

Dependability Cases

Dependability Cases

Dependability Modeling with the Architecture Analysis & Design Language (AADL)

Dependability Modeling with the Architecture Analysis & Design Language (AADL)

Design Specifications for ADAptive Real-Time Systems

The design specification method described in this report treats a software architecture as a set of run-time entities, including tasks and external input/output elements, which interact either via messages or shared data structures. Tasks have a single thread of execution and represent program units that may be executed concurrently. External input elements produce input requests which in turn trigger a set of low level activities to be executed by tasks. External output elements consume results which are produced by tasks. The specification method discussed here facilitates the description of the dynamic structure of run-time entities, the synchronization and communication between these entities, and their resource consumption and production properties (which include timing and sizing).

Diagrams and Languages for Model-Based Software Engineering of Embedded Systems UML and AADL

Diagrams and Languages for Model-Based Software Engineering of Embedded Systems UML and AADL

Distributed Real-Time System Design: Theoretical Concepts and Applications

Distributed real-time system design raises new theoretical issues and application challenges, beyond those of centralized systems. Rate monotonic scheduling (RMS) theory has been successfully applied in the scheduling of centralized systems. RMS and its generalizations have been adopted by national high technology projects such as the Space Station and has recently been supported by major open standards such as the IEEE Futurebus+ and POSIX.4. In this paper, we describe the use of generalized rate monotonic scheduling theory for the design and analysis of a distributed real-time system. We review the recent extensions of the theory to distributed system scheduling, examine the architectural requirements for use of the theory, and finally provide an application example.

Distributed System Design Using Generalized Rate Monotonic Theory

In this paper, we describe the use of generalized rate monotonic scheduling theory for the design and analysis of a distributed real-time system. We review the theory, examine the architectural requirements for the use of the theory, and finally provide an application example.

Embedded Systems Architecture Analysis Using SAE AADL

Embedded Systems Architecture Analysis Using SAE AADL

Engineering Performance-Critical Systems: meeting and exceeding performance, dependability, and interoperability goals

Engineering Performance-Critical Systems: meeting and exceeding performance, dependability, and interoperability goals

Evolving Persistent Objects in a Distributed Environment

This paper considers a class of objects, called incrementally mutable objects, that are intermediate between mutable and immutable objects. Intuitively, the only permitted modifications to an incrementally mutable object are those that add new information to the object while preserving existing information. Changes to incrementally mutable objects do not require central synchronization. When a network becomes partitioned, the same incrementally mutable object can be safely modified in each subnetwork. A mutable object can be modeled by a set of immutable objects that represent each value of the object over time and an incrementally mutable object that relates each immutable object to its successor. Multiple successors are permitted to represent parallel changes.

Experiences Porting the Distributed ADA Real-Time Kernel

The Distributed ADA Real-Time Kernel (DARK) is a mechanism for supporting the execution of distributed real-time ADA applications in embedded computer systems. It provides a solution to scheduling and distributing tasks without modifying the ADA language or vendor-supplied run time systems. An important test of the utility of the Kernel is whether or not it can be ported to different hardware architectures and still function effectively. As part of an independent research and development project, Boeing Military Airplanes and The Wichita State University became co-acceptors of a copy of DARK for the purpose of demonstrating a port to a 68000-based distributed architecture. This technical report describes the experiences in accomplishing the port.

Fault Tolerant Systems Practitioner's Workshop June 10-11, 1991

On June 10-11, 1991, a Fault Tolerant Systems Practitioner's Workshop was held at the Software Engineering Institute. The purpose of the workshop was to attempt to identify how fault tolerance is being applied today, why fault tolerance is under used, and what can be done to bring fault tolerant practices into wider use. Attendance at the workshop was limited to a small number of practitioners who had successfully applied fault tolerance in a systems context. This report summarizes the proceedings of the workshop which included a discussion of barriers to the deployment of fault tolerant systems, a summary of the state of the practice, and a discussion of the technology needs of fault tolerance. The report concludes with a discussion of ways the Software Engineering Institute may be able to help bring fault tolerant practices into wider use.

Flow Latency Analysis with the Architecture Analysis and Design Language (AADL)

Flow Latency Analysis with the Architecture Analysis and Design Language (AADL)

Formal Specification and Verification of Concurrent Programs

This module introduces formal specification of concurrent software and verification of the consistency between concurrent programs and their specifications. First, what one might want to be able to prove about a concurrent program is discussed.

Formal Verification of Programs

This module introduces formal verification of programs. It deals primarily with proofs of sequential programs, but also with consistency proofs for data types and deduction of particular behaviors of programs from their specifications. Two approaches are considered: verification after implementation that a program is consistent with its specification, and parallel development of a program and its specification. An assessment of formal verification is provided.

Framework Document: Model-Based Verification Pilot Study

This Pilot Study Framework document describes the processes, activities, artifacts, and deliverables associated with an Engineering Practice Investigation of Model-Based Verification (MBV).

Functional Performance Specification for an External Computer System Simulator

This document defines the functional and performance requirements for the inertial navigation system simulator that interfaces with the external computer system (ECS) simulator.

Functional Performance Specification for an Inertial Navigation System

This document defines the functional and performance requirements for the inertial navigation system simulator that interfaces with the external computer system (ECS) simulator. Both the INS simulator and the ECS simulator are being developed in ADA by the Real-Time Embedded Systems Testbed Project at the Software Engineering Institute. The INS simulator is similar to a real-world INS, but has reduced functionality. This document provides specifications for the major functions of the INS simulator.

Generic Avionics Software Specification

This report informally specifies the general functions, data interactions, and timing constraints for an avionics mission control computer system typical of those found in some existing U.S. Navy/Marine Corps aircraft.

Governance Issues for a Service-Oriented Architecture

Governance Issues for a Service-Oriented Architecture

Hartstone Benchmark Results and Analysis

Hartstone Benchmark Results and Analysis

Hartstone: Synthetic Benchmark Requirements for Hard Real-Time Applications

The purpose of this paper is to define the operational concept for a series of benchmark requirements to be used to test the ability of a system to handle hard real-time applications. Implementations of such benchmarks would be useful in evaluating scheduling algorithms, protocols, and design paradigms, as well as processors, languages, compilers, and operating systems. Several ADA programs are under development to test standard versions of the benchmark requirements and will be released into the public domain.

Implementing Priority Inheritance Algorithms in an ADA Runtime System

This paper presents a high-level design-in the form of necessary data structures, mechanisms, and algorithms-for implementing the basic priority inheritance and priority ceiling protocols in an ADA runtime system.

Implementing Sporadic Servers in ADA

The purpose of this paper is to present the data structures and algorithms for implementing sporadic servers in real-time systems programmed in ADA.

Improving Predictability in Embedded Real-Time Systems

Improving Predictability in Embedded Real-Time Systems

Introduction to Software Engineering Practices Using Model-Based Verification, An

This is an introductory report on the use of model-based verification techniques within software development and upgrade practices.

Introduction to Software Verification and Validation

This curriculum module provides an overview needed to understand in-depth curriculum modules in the verification and validation area.

Issues in Real-Time Data Management

This report explores issues related to the use of database management technology in support of real-time systems programming. It describes the potential benefits of database support for real-time systems, and it describes the state of the art in database technologies relevant to real-time. The report concludes that more research and development will be needed before the benefits of database management can be applied to real-time system development.

Learn to use the SAE AADL Standard Model-Based Engineering with SAE AADL

Learn to use the SAE AADL Standard Model-Based Engineering with SAE AADL

Managing Risks in Modernizing Legacy Systems

Managing Risks in Modernizing Legacy Systems

Mode Change Protocols for Priority-Driven Preemptive Scheduling

This paper discusses a protocol for systematically accomplishing mode change in the context of a priority-driven preemptive scheduling environment.

Model-Based Verification: A Technology for Dependable Upgrade

This is a preliminary report on the technological foundations of model-based verification for engineering software system upgrades.

Model-Based Verification: Abstraction Guidelines

Model-Based Verification: Abstraction Guidelines

Model-Based Verification: An Engineering Practice

Model-Based Verification: An Engineering Practice

Model-Based Verification: Analysis Guidelines

This technical note provides guidance for the analysis activity that occurs during the interpretation of results produced by model-checking tools.

Model-Based Verification: Claim Creation Guidelines

Model Based Verification (MBV) is a systematic approach to finding defects (errors) in software requirements, designs, or code. MBV involves creating essential models of system behavior and analyzing these models against formal representations of expected properties, known as claims. Claim generation has been identified as a particularly complex activity within model-based verification. This technical note describes a pattern-based approach to facilitate claim generation. The report includes a list of directly usable patterns for the most frequent expected properties found in system specifications.

Model-Based Verification: Guidelines for Generating Expected Properties

Model-Based Verification: Guidelines for Generating Expected Properties

Model-Based Verification: Scope, Formalism, and Perspective Guidelines

The goal of model-based verification (MBV) is to reduce the number of defects. Like any other quality assurance (QA) technique, it is not equally efficient in every situation. It is critical to determine where and how to use MBV to achieve the largest impact in terms of the number and criticality of defects found with a reasonable amount of effort. This document provides guidance for defining the scope, formalism (approach and tools), and perspective for applying MBV. The critical (important or risky) aspects of the system and its development, including both programmatic and technical issues, drive these choices and form the basis for these guidelines.

Modeling of System Families

Modeling of System Families

Modeling the Space Shuttle Liquid Hydrogen Subsystem

Modeling the Space Shuttle Liquid Hydrogen Subsystem

OOD Paradigm for Flight Simulators (2nd Edition), An

This report presents a paradigm for object-oriented implementation of flight simulators. It is a result of work on the ADA Simulator Validation Program (ASV) carried out by members of the technical staff at the SEI.

On System Scalability

On System Scalability

Performance and Reliability Enhancement of the Durra Runtime Environment

Performance and Reliability Enhancement of the Durra Runtime Environment

Perspective on the State of Research in Fault-Tolerant Systems, A

As computers take on a greater role in society, their dependability is becoming increasingly important. Given software's critical role in computing systems, reliable software has emerged as crucial to achieving a dependable infrastructure. Using a system perspective that recognizes the prominence of software, we characterize the current state of fault-tolerance research as it contributes to the dependability of computer systems and we conjecture on future directions for this research area.

Predictable, Model-Based Engineering for Embedded Systems

Predictable, Model-Based Engineering for Embedded Systems

Priority Ceiling Protocol: A Method for Minimizing the Blocking of High-Priority ADA Tasks, The

The priority ceiling protocol is a new technique that addresses the priority inversion problem, i.e., the possibility that a high-priority task can be delayed by a low-priority task. Under the priority ceiling protocol, a high priority task can be blocked at most once by a lower priority task. This paper defines how to apply the protocol to ADA. In particular, restrictions on the use of task priorities in ADA are defined as well as restrictions on the use of ADA tasking constructs. An extensive example illustrating the behavior guaranteed by the protocol is given.

Proceedings of the Real-Time Systems Engineering Workshop

This report presents the results of a workshop on the topic of real-time systems engineering. The workshop was held as part of the SEI Symposium in Washington, DC, during September 2000. The objective of the workshop was to identify key issues and obtain feedback from attendees concerning real-time systems engineering. Two broad keynote presentations were presented, followed by topical presentations concerning predictability, fault tolerance, and interoperability. This report summarizes the workshop in terms of foundation, management, and technical topics, and it contains a discussion related to developing a community of interest for real-time systems engineering.

Prototype Real-Time Monitor: ADA Code

This report documents the ADA code of the prototype real-time monitor (RTM).

Prototype Real-Time Monitor: Design

The requirements imposed by flight simulators and good software engineering practice on Ada systems force software engineers to seek new solutions to the problem of monitoring executing software. This report examines some of these requirements and, based on these requirements, defines a subset for implementation as a prototype real-time monitor (RTM).

Prototype Real-Time Monitor: Executive Summary

This report summarizes the history, goals, and conclusions of the prototype real-time monitor development effort.

Prototype Real-Time Monitor: Requirements

The requirements imposed by flight simulators and good software engineering practice on Ada systems force software engineers to seek new solutions to the problem of monitoring executing software. This report examines some of these requirements and, based on these requirements, defines a subset for implementation as a prototype real-time monitor (RTM).

Prototype Real-Time Monitor: User's Manual

Prototype Real-Time Monitor: User's Manual

Rate Monotonic Analysis for Real-Time Systems

In this report, we review important decisions in the development of RMA. Our experience indicates that technology transition considerations should be embedded in the process of technology development from the start, rather than as an afterthought.

Rate Monotonic Analysis for Real-Time Systems: Instructor's Guide

This educational materials package has been developed for instructors of software engineering and, more specifically, real-time systems. This package will help instructors teach rate monotonic analysis (RMA) to graduate and undergraduate software, computer, and electrical engineering students. The package can also be used to teach RMA to continuing education students. The presentation materials and exercises included have been used by Ruth Ravenel in both graduate and undergraduate courses.

Real-Time Application Development with OSEK: A Review of the OSEK Standards

Real-Time Application Development with OSEK: A Review of the OSEK Standards

Real-Time Locking Protocol, A

When a database system is used in a real-time application, the concurrency control protocol must satisfy not only the consistency of shared data but also the timing constraints of the application. In this paper, we examine a priority-driven two-phase lock protocol called the read- or write-priority ceiling protocol. We show that this protocol is free of deadlock, and in addition a high-priority transaction can be blocked by lower priority transactions for at most the duration of a single embedded transaction. We then evaluate system performance experimentally.

Real-Time Scheduling Theory and ADA

Real-Time Scheduling Theory and ADA

Real-Time Scheduling Theory and ADA (1988)

The ADA tasking model was intended to facilitate the management of concurrency in a priority-driven scheduling environment. In this paper, we will review some important results of a priority-based scheduling theory, illustrate its applications with examples, discuss its implications for the ADA tasking model, and suggest workarounds that permit us to implement analytical scheduling algorithms within the existing framework of ADA.

Real-Time Software Engineering in ADA: Observations and Guidelines

Two important aspects of developing a real-time system are controlling devices and managing concurrency. In this report, we present several techniques for controlling devices with ADA and several ADA tasking paradigms for managing concurrency. The material presented in this report is taken from our experiences in developing a real-time embedded system in ADA, and we use examples from this system to illustrate the various methods we present. We begin by describing our experiences using ADA to control devices. Specifically, we identify issues related to accessing device registers and handling interrupts, and present techniques for dealing with such issues. We then recount our experiences using ADA to manage concurrency. Specifically, we present coding paradigms for implementing periodicity and constructing synchronization mechanisms. We illustrate analytical methods for determining the schedulability of a task set. We then discuss the effect of aperiodic processing requirements on the schedulability of a task set.

Real-Time Systems Engineering: Lessons Learned from Independent Technical Assessments

The Software Engineering Institute (SEI) has performed several Independent Technical Assessments (ITAs) on mission-critical/real-time systems for the Department of Defense and other agencies. This paper contains observations, recurring themes, trends, and lessons learned about systems development as derived from real-time/mission-critical programs that have been reviewed over the last three years. It is hoped that the observations contained in this paper will be of value to future program managers and help ensure their success.

SAE Architecture Analysis and Design Language Fact Sheet

The SAE AADL is an international standard for predictable model-based engineering 
of real-time and embedded computer systems.

Safety-Critical Software: Status Report and Annotated Bibliography

Many systems are deemed safety-critical and these systems are increasingly dependent on software. Much has been written in the literature with respect to system and software safety. This report summarizes some of that literature and outlines the development of safety-critical software. Techniques for hazard identification and analysis are discussed. Further, techniques for the development of safety-critical software are mentioned. A partly annotated bibliography of literature concludes the report.

Scheduling Sporadic and Aperiodic Events in a Hard Real-Time System

A real-time system consists of both aperiodic and periodic tasks. Periodic tasks have regular arrival times and hard deadlines. Aperiodic tasks have irregular arrival times and either soft or hard deadlines. In this paper, we present a new algorithm, the Sporadic Server algorithm, that greatly improves response times for soft-deadline aperiodic tasks and can guarantee hard deadlines for both periodic and aperiodic tasks. The operation of the Sporadic Server algorithm, its performance, and schedulability analysis are discussed and compared with previous, published aperiodic service algorithms.

Second International Conference on COTS-Based Software Systems

Second International Conference on COTS-Based Software Systems

Simplex Architecture Performance and Cost

The Simplex Architecture facilitates the building of dependable and upgradable real-time systems. Before using the technology, potential users want to know more about the costs of adopting the Simplex paradigm compared to the benefits of using it. This paper examines Simplex performance and the costs associated with its use.

Simplex in a Hostile Communications Environment: The Coordinated Prototype

This report describes an approach to using Simplex to construct a COTS-based computer system capable of coordinated real-time motion control in a hostile communications environment.

Specifying Functional and Timing Behavior for Real-Time Applications

We present a notation and a methodology for specifying the functional and timing behavior of real-time applications for a heterogeneous machine. In our methodology, we build upon well-defined, though isolated, pieces of previous work: Larch and Real-Time Logic. In our notation, we strive to keep separate the functional specification from the timing specification so that a task's functionality can be understood independent of its timing behavior. We show that while there is a clean separation of concerns between these two specifications, the semantics of both pieces as well as their combination are simple.

State of the Practice Report: Problems in the Practice of Performance Engineering

As systems have performance requirements, sometimes dominant and explicit, and other times subordinate and implicit. Despite the pervasiveness and importance of performance requirements, performance problems persist. To help us understand why, we sponsored a workshop in performance engineering and conducted some structured interviews with software contractors. This report summarizes our observations.

Study in the Use of CORBA in Real-Time Settings: Model Problems for the Manufacturing Domain, A

In this report, we describe the application of an off-the-shelf ORB to two real-time model problems.

Study of Practice Issues in Model-Based Verification Using the Symbolic Model Verifier (SMV), A

This report presents the results of a study on the practice issues involved in using the Symbolic Model Verifier (SMV) for model checking software systems.

Survey of Real-Time Performance Benchmarks for the Ada Programming Language, A

This survey provides a summary description of some of the major Ada benchmarks currently available and an evaluation of their applicability to the Real-Time Embedded Systems Testbed Project at the SEI. The benchmarks discussed are the University of Michigan benchmarks, the ACM Performance Issues Working Group (PIWG) benchmarks, and the prototype Ada Compiler Evaluation Capability (ACEC) of the Institute for Defense Analyses (IDA).

The Architecture Analysis & Design Language (AADL): An Introduction

The Architecture Analysis & Design Language (AADL): An Introduction

The SAE Avionics Architecture Description Language (AADL) Standard: A Basis for Model-Based Architecture-Driven Embedded Systems Engineering

The SAE Avionics Architecture Description Language (AADL) Standard: A Basis for Model-Based Architecture-Driven Embedded Systems Engineering

Three Perspectives Required of Service-Oriented Architectures

Three Perspectives Required of Service-Oriented Architectures

Three Perspectives of Service-Oriented Architectures

Three Perspectives of Service-Oriented Architectures

Towards an Assurance Case Practice for Medical Devices

This report explores how the assurance case promises a technology answer for the challenge that manufacturers and federal regulators face in gaining confidence about the performance of software-dominated medical devices.

Use of ASN.1 and XDR for Data Representation in Real-Time Distributed Systems, The

This report provides an overview of two standards that are used for data specification and representation in distributed systems.

Using Model-Based Engineering and Architectural Models to Build Secure Systems

Using Model-Based Engineering and Architectural Models to Build Secure Systems

VAXELN Experimentation: Programming a Real-Time Periodic Task Dispatcher Using VAXELN ADA 1.1

The purpose of this paper is to provide the reader with some technical information and observations ADA source code, and measurement results based on experimentation with respect to developing a real-time periodic task dispatcher in ADA.

VAXELYN Experimentation: Programming a Real-Time Clock and Interrupt Handling Using VAXELYN ADA 1.1

This report describes the results of implementing an interrupt handler totally in ADA for a MicroVAX II/VAXELN 2.3 target system, the VAXELN 1.1 ADA compiler, and a KWV11-C programmable real-time clock.

Workshop on the State of the Practice in Dependably Upgrading Critical Systems

This report describes the results of the Workshop on the State of the Practice in Dependably Upgrading Critical Systems held April 16-17, 1997 at the Software Engineering Institute.