Richard E. Schantz

Bio: Richard E. Schantz is an academic researcher from BBN Technologies. The author has contributed to research in topics: Middleware (distributed applications) & Middleware. The author has an hindex of 27, co-authored 83 publications receiving 3336 citations. Previous affiliations of Richard E. Schantz include University of Illinois at Urbana–Champaign.

Architectural support for quality of service for CORBA objects

Abstract: CORBA is a commercial standard for distributed object computing which shows great promise in the development of distributed programs. Its interface description language (IDL) enables objects to be developed independently of the underlying programming language, operating system, or computer architecture on which they will execute. While this is sufficient in many environments, programs deployed in a wide-area distributed system encounter conditions which are much more hostile and varying than those operating in a single address space or within a single local area network. In this paper we discuss four major problems we have observed in our developing and deploying wide-area distributed object applications and middleware. First, most programs are developed ignoring the variable wide area conditions. Second, when application programmers do try to handle these conditions, they have great difficulty because these harsh conditions are different from those of the local objects they are used to dealing with. Third, IDL hides information about the tradeoffs any implementation of an object must make. Fourth, there is presently no way to systematically reuse current technology components which deal with these conditions, so code sharing becomes impractical. In this paper we also describe our architecture, Quality of Service for CORBA Objects (QuO), which we have developed to overcome these limitations and integrate their solution by providing QoS abstractions to CORBA objects. First, it makes these conditions first class entities and integrates knowledge of them over time, space, and source. Second, it reduces their variance by masking. Third, it exposes key design decisions of an object's implementation and how it will be used. Fourth, it supports reuse of various architectural components and automatically generates others. © 1997 John Wiley & Sons, Inc.

AQuA: an adaptive architecture that provides dependable distributed objects

Abstract: Dependable distributed systems are difficult to build. This is particularly true if they have dependability requirements that change during the execution of an application, and are built with commercial off-the-shelf hardware. In that case, fault tolerance must be achieved using middleware software, and mechanisms must be provided to communicate the dependability requirements of a distributed application to the system and to adapt the system's configuration to try to achieve the desired dependability. The AQuA architecture allows distributed applications to request a desired level of availability using the Quality Objects (QuO) framework and includes a dependability manager that attempts to meet requested availability levels by configuring the system in response to outside requests and changes in system resources due to faults. The AQuA architecture uses the QuO runtime to process and invoke availability requests, the Proteus dependability manager to configure the system in response to faults and availability requests, and the Ensemble protocol stack to provide group communication services. Furthermore, a CORBA interface is provided to application objects using the AQuA gateway. The gateway provides a mechanism to translate between process-level communication, as supported by Ensemble, and IIOP messages, understood by Object Request Brokers. Both active and passive replication are supported, and the replication type to use is chosen based on the performance and dependability requirements of particular distributed applications.

High-performance, massively scalable distributed systems using the MapReduce software framework: the SHARD triple-store

Abstract: In this paper we discuss the use of the MapReduce software framework to address the challenge of constructing high-performance, massively-scalable distributed systems. We discuss several design considerations associated with constructing complex distributed systems using the MapReduce software framework, including the difficulty of scalably building indexes. We focus on Hadoop, the most popular MapReduce implementation. Our discussion and analysis are motivated by our construction of SHARD, a massively scalable, high-performance and robust triple-store technology on top of Hadoop. We provide a general approach to construct an information system from the MapReduce software framework that responds to data queries. We provide experimental results generated of an early version of SHARD. We close with a discussion of hypothetical MapReduce alternatives that can be used for the construction of more scalable distributed computing systems.

Middleware for Distributed Systems Evolving the Common Structure for Network-centric Applications

Abstract: Two fundamental trends influence the way we conceive and construct new computing and information systems The first is that information technology of all forms is becoming highly commoditized ie, hardware and software artifacts are getting faster, cheaper, and better at a relatively predictable rate The second is the growing acceptance of a network-centric paradigm, where distributed applications with a range of quality of service (QoS) needs are constructed by integrating separate components connected by various forms of communication services The nature of this interconnection can range from 1 The very small and tightly coupled, such as avionics mission computing systems to 2 The very large and loosely coupled, such as global telecommunications systems The interplay of these two trends has yielded new architectural concepts and services embodying layers of middleware These layers are interposed between applications and commonly available hardware and software infrastructure to make it feasible, easier, and more cost effective to develop and evolve systems using reusable software Middleware stems from recognizing the need for more advanced and capable support–beyond simple connectivity–to construct effective distributed systems A significant portion of middleware-oriented R&D activities over the past decade have focused on 1 The identification, evolution, and expansion of our understanding of current middleware services in providing this style of development and 2 The need for defining additional middleware layers and capabilities to meet the challenges associated with constructing future network-centric systems These activities are expected to continue forward well into this decade to address the needs of next-generation distributed applications

Specifying and measuring quality of service in distributed object systems

Abstract: Distributed applications are difficult to build and maintain and are even more difficult when the applications are distributed over wide-area networks. Distributed Object Computing middleware has emerged to simplify the building of distributed applications by hiding implementation details behind functional interfaces. However, critical applications have non-functional requirements, such as real-time performance, dependability, or security, that are as important as the functional requirements, but are also hidden by the middleware. Because current distributed object middleware doesn't support these aspects of critical applications, application developers often find themselves bypassing the distributed object systems, effectively gaining little or no advantage from the middleware. We have developed Quality Objects (QuO), a framework for including Quality of Service (QoS) in distributed object applications. QuO supports the specification of QoS contracts between clients and service providers, runtime monitoring of contracts, and adaptation to changing system conditions. A crucial aspect of QuO is a suite of Quality Description Languages for describing states of QoS, system elements that need to be monitored to measure the current QoS, and notification and adaptation to trigger when the state of QoS in the system changes. This paper gives a brief overview of QuO and describes the syntax and semantics of CDL, the component of QDL for describing QoS contracts.

An overview of AspectJ

Abstract: Aspect] is a simple and practical aspect-oriented extension to Java With just a few new constructs, AspectJ provides support for modular implementation of a range of crosscutting concerns. In AspectJ's dynamic join point model, join points are well-defined points in the execution of the program; pointcuts are collections of join points; advice are special method-like constructs that can be attached to pointcuts; and aspects are modular units of crosscutting implementation, comprising pointcuts, advice, and ordinary Java member declarations. AspectJ code is compiled into standard Java bytecode. Simple extensions to existing Java development environments make it possible to browse the crosscutting structure of aspects in the same kind of way as one browses the inheritance structure of classes. Several examples show that AspectJ is powerful, and that programs written using it are easy to understand.

[서평]「Applied Cryptography」

Abstract: The objective of this paper is to give a comprehensive introduction to applied cryptography with an engineer or computer scientist in mind. The emphasis is on the knowledge needed to create practical systems which supports integrity, confidentiality, or authenticity. Topics covered includes an introduction to the concepts in cryptography, attacks against cryptographic systems, key use and handling, random bit generation, encryption modes, and message authentication codes. Recommendations on algorithms and further reading is given in the end of the paper. This paper should make the reader able to build, understand and evaluate system descriptions and designs based on the cryptographic components described in the paper.

Self-adaptive software: Landscape and research challenges

Abstract: Software systems dealing with distributed applications in changing environments normally require human supervision to continue operation in all conditions. These (re-)configuring, troubleshooting, and in general maintenance tasks lead to costly and time-consuming procedures during the operating phase. These problems are primarily due to the open-loop structure often followed in software development. Therefore, there is a high demand for management complexity reduction, management automation, robustness, and achieving all of the desired quality requirements within a reasonable cost and time range during operation. Self-adaptive software is a response to these demands; it is a closed-loop system with a feedback loop aiming to adjust itself to changes during its operation. These changes may stem from the software system's self (internal causes, e.g., failure) or context (external events, e.g., increasing requests from users). Such a system is required to monitor itself and its context, detect significant changes, decide how to react, and act to execute such decisions. These processes depend on adaptation properties (called self-a properties), domain characteristics (context information or models), and preferences of stakeholders. Noting these requirements, it is widely believed that new models and frameworks are needed to design self-adaptive software. This survey article presents a taxonomy, based on concerns of adaptation, that is, how, what, when and where, towards providing a unified view of this emerging area. Moreover, as adaptive systems are encountered in many disciplines, it is imperative to learn from the theories and models developed in these other areas. This survey article presents a landscape of research in self-adaptive software by highlighting relevant disciplines and some prominent research projects. This landscape helps to identify the underlying research gaps and elaborates on the corresponding challenges.

System and method for simultaneous display of multiple information sources

Abstract: A computerized method of presenting information from a variety of sources on a display device. Specifically the present invention describes a graphical user interface for organizing the simultaneous display of information from a multitude of information sources. In particular, the present invention comprises a graphical user interface which organizes content from a variety of information sources into a grid of tiles, each of which can refresh its content independently of the others. The grid functionality manages the refresh rates of the multiple information sources. The present invention is intended to operate in a platform independent manner.