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The interpretations of logical expressions found in most introductory textbooks are not suitable for use in software engineering applications because they do not deal with partial functions. More advanced papers and texts deal with partial functions in a variety of complex ways. This paper proposes a very simple change to the classic interpretation of predicate expressions, one that defines their value for all values of all variables, yet is almost identical to the standard definitions. It then illustrates the application of this interpretation in software documentation. [ABSTRACT FROM AUTHOR]

The formalism of temporal logic has been suggested to be an appropriate tool for expressing the semantics of concurrent programs. This paper is concerned with the application of temporal logic to the specification of factors affecting the synchronization of concurrent processes. Towards this end, we first introduce a model for synchronization and axiomatize its behavior. SYSL, a very high-level language for specifying synchronization properties, is then described. It is designed using the primitives of temporal logic and features constructs to express properties that affect synchronization in a fairly natural and modular fashion. Since the statements in the language have intuitive interpretations, specifications are humanly readable. In addition, since they possess appropriate formal semantics, unambiguous specifications result. [ABSTRACT FROM AUTHOR]

This paper discusses the goals and methods of the Toolpack project and in this context discusses the architecture and design of the software system being produced as the focus of the project. Toolpack is presented as an experimental activity in which a large software tool environment is being created for the purpose of general distribution and then careful study and analysis. The paper begins by explaining the motivation for building integrated tool sets. It then proceeds to explain the basic requirements that an integrated system of tools must satisfy in order to be successful and to remain useful both in practice and as an experimental object. The paper then summarizes the tool capabilities that will be incorporated into the environment. It then goes on to present a careful description of the actual architecture of the Toolpack integrated tool system. Finally the Toolpack project experimental plan is presented, and future plans and directions are summarized. [ABSTRACT FROM AUTHOR]

Although the benefits of requirements traceability are widely recognized, the actual practice of maintaining a traceability scheme is not always entirely successful. The traceability infrastructure underlying a software system tends to erode over its lifetime, as time-pressured practitioners fail to consistently maintain links and update impacted artifacts each time a change occurs, even with the support of automated systems. This paper proposes a new method of traceability based upon event-notification and is applicable even in a heterogeneous and globally distributed development environment. Traceable artifacts are no longer tightly coupled but are linked through an event service, which creates an environment in which change is handled more efficiently, and artifacts and their related links are maintained in a restorable state. The method also supports enhanced project management for the process of updating and maintaining the system artifacts. [ABSTRACT FROM AUTHOR]

Software productivity has been steadily increasing over the past 30 years, but not enough to close the gap between the demands placed on the software industry and what the state of the practice can deliver [22], [39]; nothing short of an order of magnitude increase in productivity will extricate the software industry from its perennial crisis [39], 1671. Several decades of intensive research in software engineering and artificial intelligence left few alternatives but software reuse as the (only) realistic approach to bring about the gains of productivity and quality that the software industry needs. In this paper, we discuss the implications of reuse on the production, with an emphasis on the technical challenges. Software reuse involves building software that is reusable by design and building with reusable software. Software reuse includes reusing both the products of previous software projects and the processes deployed to produce them, leading to a wide spectrum of reuse approaches, from the building blocks (reusing products) approach, on one hand, to the generative or reusable processor (reusing processes), on the other 1681. We discuss the implication of such approaches on the organization, control, and method of software development and discuss proposed models for their economic analysis. Software reuse benefits from methodologies and tools to: 1) build more readily reusable software and 2) locate, evaluate, and tailor reusable software, the last being critical for the building blocks approach. Both sets of issues are discussed in this paper, with a focus on application generators and OO development for the first and a thorough discussion of retrieval techniques for software components, component composition (or bottom-up design), and transformational systems for the second. We conclude by highlighting areas that, in our opinion, are worthy of further investigation. [ABSTRACT FROM AUTHOR]

This paper describes a new method, called mutant unification, for high-performance software testing. The method is aimed at supporting program mutation on parallel machines based on the Single Instruction Multiple Data stream (SIMD) paradigm. Several parameters that affect the performance of unification have been identified and their effect on the time to completion of a mutation test cycle and speedup has been studied. Program mutation analysis provides an effective means for determining the reliability of large software systems. It also provides a systematic method for measuring the adequacy of test data. However, it is likely that testing large software systems using mutation is computation bound and prohibitive on traditional sequential machines. Current implementations of mutation tools are unacceptably slow and are only suitable for testing relatively small programs. The unification method reported in this paper provides a practical alternative to the current approaches. It also opens up a new application domain for SIMD machines. [ABSTRACT FROM AUTHOR]

RTAG is a language based on an attribute grammar notation for specifying protocols. Its main design goals are: 1) to support concise and easily understood expression of complex real-world protocols, and 2) to serve as the basis of a portable software system for automated protocol implementation. This paper summarizes the RTAG language, gives examples of its use, sketches the algorithms used in generating implementations from these specifications, and describes a UNIX®-based automated implementation system for RTAG. [ABSTRACT FROM AUTHOR]

In today's distributed computing environment, the coordination of concurrent processes and the coordination of resource sharing are of critical importance. Consequently, much effort has been focused on the modeling of problems of coordination and concurrency. In this paper we describe a software environment (SPANNER) for the specification and analysis of such problems. In the SPANNER environment, one can formally produce a specification of a distributed computing problem, and then verify its "correctness" through reachability analysis and simulation. SPANNER is based on a finite state machine model called the selection/resolution model. We illustrate the capabilities of SPANNER by specifying and analyzing two classical coordination problems: 1) the dining philosophers; and 2) Dijkstra's concurrent programming problem. In addition to discussing these specific problems, our intention is also to focus on some of the more recently implemented capabilities of the SPANNER system such as process types and cluster variables. [ABSTRACT FROM AUTHOR]

Managing software engineering projects requires an ability to comprehend and balance the technological, economic, and social bases through which large software systems are developed. It requires people who can formulate strategies for developing systems in the presence of ill-defined requirements, new computing technologies, and recurring dilemmas with existing computing arrangements. This necessarily assumes skill in acquiring adequate computing resources, controlling projects, coordinating development schedules, and employing and directing competent staff. It also requires people who can organize the process for developing and evolving software products with locally available resources. Managing software engineering projects is as much a job of social interaction as it is one of technical direction. This paper examines the social arrangements that a soft- ware manager must deal with in developing and using new computing systems, evaluating the appropriateness of software engineering tools or techniques, directing the evolution of a system through its life cycle, organizing and staffing software engineering projects, and assessing the distributed costs and benefits of local software engineering practices. The purpose is to underscore the role of social analysis of software engineering practices as a cornerstone in understanding what it takes to productively manage software projects. [ABSTRACT FROM AUTHOR]

Testing has long been in need of mathematical underpinnings to explain its value as well as its limitations. This paper develops and applies a mathematical framework that 1) unifies previous work on the subject, 2) provides a mechanism for comparing the power of methods of testing programs based on the degree to which the methods approximate program verification, and 3) provides a reasonable and useful interpretation of the notion that successful tests increase one's confidence in the program's correctness. Applications of the framework include confirmation of a number of common assumptions about practical testing methods. Among the assumptions confirmed is the need for generating tests from specifications as well as programs. On the other hand, a careful formal analysis of the usual assumptions surrounding mutation analysis shows that the "competent programmer hypothesis" does not suffice to ensure the claimed high reliability of mutation testing. Hardware testing is shown to fit into the framework as well, and a brief consideration of it shows how the practical differences between it and software testing arise. [ABSTRACT FROM AUTHOR]

Computations of distributed systems are extremely difficult to specify and verify using traditional techniques because the systems are inherently concurrent, asynchronous, and nondeterministic. Furthermore, computing nodes in a distributed system may be highly independent of each other, and the entire system may lack an accurate global clock. In this paper, we develop an event-based model to specify formally the behavior (the external view) and the structure (the internal view) of distributed systems. Both control-related and data-related properties of distributed systems are specified using two fundamental relationships among events: the "precedes" relation, representing time order; and the "enables" relations, representing causality. No assumption about the existence of a global clock is made in the specifications. The specification technique has a rather wide range of applications. Examples from different classes of distributed systems, include communication systems, process control systems, and a distributed prime number generator, are used to demonstrate the power of the technique. The correctness of a design can be proved before implementation by checking the consistency between the behavior specification and the structure specification of a system. Both safety and liveness properties can be specified and verified. Furthermore, since the specification technique defines the orthogonal properties of a system separately, each of them can then be verified independently. Thus, the proof technique avoids the exponential state-explosion problem found in state-machine specification techniques. [ABSTRACT FROM AUTHOR]

A fundamental step in the software design process is the selection of a refinement (implementation) for a data abstraction. This step traditionally involves investigating the expected performance of a system under different refinements of an abstraction and then selecting a single alternative which minimizes some performance cost metric. In this paper we reformulate this design step to allow different refinements of the same data abstraction within a computation. This reformulation reflects the fact that the implementation appropriate for a data abstraction is dependent on the behavior exhibited by the objects of the abstraction. Since this behavior can vary among the objects of a computation, a single refinement is often inappropriate. Accordingly, three frameworks are presented for understanding and representing variations in the behavior of objects and, thus, the potential for multiple implementations. The three frameworks are based upon: 1) a static partitioning of objects into disjoint implementation classes; 2) static partitioning of classes into implementation regions; and 3) dynamic partitioning of classes into implementation regions. These frameworks and analytic tools useful in investigating expected performance under multiple implementations are described in detail. [ABSTRACT FROM AUTHOR]

This paper describes a multiview characterization of concurrent software and systems suitable for displaying and analyzing performance information. The views draw from well-known descriptions, and are compatible with established techniques and tools such as execution graphs, Petri Nets, State-Charts, structured design or object-oriented design, and various models for performance. The views are connected by means of a "Core model" and are used together to extract information relating to system integration, such as interprocess overheads, and the delay behavior of separate software components in complex systems. The integration of the views in the Core assists by converting results in one view (such as scheduling delay for resources) to parameters in another (such as delays along a path). The ultimate goal of the views is to support designers in making tradeoffs which involve performance, and to provide early assessment of the performance potential of software designs. [ABSTRACT FROM AUTHOR]

Software bottlenecks are performance constraints caused by slow execution of a software task. In typical client-server systems a client task must wait in a blocked state for the server task to respond to its requests, so a saturated server will slow down all its clients. A Rendezvous Network generalizes this relationship to multiple layers of servers with send-and-wait interactions (rendezvous), a two-phase model of task behavior, and to a unified model for hardware and software contention. Software bottlenecks have different symptoms, different behavior when the system is altered, and a different cure from the conventional bottlenecks seen in queueing network models of computer systems, caused by hardware limits. The differences are due to the "push-back" effect of the rendezvous, which spreads the saturation of a server to its clients. The paper describes software bottlenecks by examples, gives a definition, shows how they can be located and alleviated, and gives a method for estimating the performance benefit to be obtained. Ultimately, if all the software bottlenecks can be removed, the performance limit will be due to a conventional hardware bottleneck. [ABSTRACT FROM AUTHOR]

Distributed applications written in Hermes typically consist of a large number of sequential processes. The use of a hierarchy of process clusters can facilitate the debugging of such applications. Ideally, such a hierarchy should be derived automatically. This paper discusses two approaches to automatic process clustering, one analyzing runtime information with a statistical approach and one utilizing additional semantic information. Tools realizing these approaches were developed and a quantitative measure to evaluate process clusters is proposed. The results obtained under both approaches are compared, and indicate that the additional semantic information improves the cluster hierarchies derived. We demonstrate the value of automatic process clustering with an example. It is shown how appropriate process clusters reduce the complexity of the understanding process, facilitating program maintenance activities such as debugging. [ABSTRACT FROM AUTHOR]

In order to effectively optimize complex programs built in a layered or recursive fashion (possibly from reused general components), the programmer has a critical need for performance information connected directly to the design decisions and other optimization opportunities present in the code. Call path refinement profiles are novel tools for guiding the optimization of such programs, that: 1) provide detailed performance information about arbitrarily nested (direct or indirect) function call sequences, and 2) focus the user's attention on performance bottlenecks by limiting and aggregating the information presented. This paper discusses the motivation for such profiles, describes in detail their implementation in the CPPROF profiler, and relates them to previous profilers, showing how most widely available profilers can be expressed simply and efficiently in terms of call path refinements. [ABSTRACT FROM AUTHOR]

The performance of transaction processing systems with two-phase locking (2PL) can be degraded by transaction blocking due to lock conflicts and aborts to resolve deadlocks. This paper develops a straightforward analytic solution method, which takes into account the variability of transaction size (the number of lock requests), an issue which has been ignored in most earlier studies. We first obtain analytic expressions for the probability of lock conflict, probability of deadlock, and the waiting time per lock conflict. We then develop a family of noniterative analytic solutions to evaluate the overall system performance by considering the expansion in transaction response time due to transaction blocking. The accuracy of these solutions is verified by validation against simulation results. We also introduce a new measure for the degree of lock contention, which is a product of the mean number of lock conflicts per transaction and the mean waiting time per lock conflict (when blocked by an active transaction). It is shown that the variability in transaction size results in an increase in both measures as compared to fixed-size transactions of comparable size. It follows that performance studies of 2PL which ignore the variability in transaction size underestimate the effect of lock contention on system performance. We also provide a solution method for the case when the processing times of transaction steps are different. The solution method is used in the analysis of the two-phase transaction processing method, according to which a transaction is first executed without requesting any locks, prefetching data (from disk) for the second execution phase with locking. In high lock contention environments, this approach may result in a significant improvement in performance compared to 2PL, which is due to the reduction in lock-holding time, since no disk 10 is required in the second phase of the execution, but this is achieved at the cost of additional CPU processing due to repeated execution. [ABSTRACT FROM AUTHOR]

This article presents information on articles published in September 1999 issue of the journal "IEEE Transactions on Software Engineering." Computer systems are used to perform many critical tasks, including guiding aircraft, scheduling railroads, assisting in surgery, controlling nuclear reactors, performing financial transactions and supporting military command and control. Although the study of these properties evolved as separate disciples, they have in common the fact that a user must have a high degree of confidence in the service that the system delivers. The first research paper in this issue of the journal considers the problem of electing a leader in a distributed system that may become partitioned. Since the partitions will not be able to communicate with each other, it is necessary to elect a leader for each partition. The second research paper addresses the problem of developing an accurate fault model that can be used to evaluate the dependability of a system. The third paper presents an approach to the quantitative evaluation of the security of operational systems.

Presents a corrected reprint of an article on logic-based approach to reverse engineering tools production.