There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

"Grid" computing has emerged as an important new field, distinguished from conventional distributed computing by its focus on large-scale resource sharing, innovative applications, and, in some cases, high performance orientation. In this article, the authors define this new field. First, they review the "Grid problem," which is defined as flexible, secure, coordinated resource sharing among dynamic collections of individuals, institutions, and resources--what is referred to as virtual organizations. In such settings, unique authentication, authorization, resource access, resource discovery, and other challenges are encountered. It is this class of problem that is addressed by Grid technologies. Next, the authors present an extensible and open Grid architecture, in which protocols, services, application programming interfaces, and software development kits are categorized according to their roles in enabling resource sharing. The authors describe requirements that they believe any such mechanisms must satisfy and discuss the importance of defining a compact set of intergrid protocols to enable interoperability among different Grid systems. Finally, the authors discuss how Grid technologies relate to other contemporary technologies, including enterprise integration, application service provider, storage service provider, and peer-to-peer computing. They maintain that Grid concepts and technologies complement and have much to contribute to these other approaches.

The Anatomy of the Grid: Enabling Scalable Virtual Organizations

物件導向軟體之架構(Object-Oriented Software Construction)探討

"Grid" computing has emerged as an important new field, distinguished from conventional distributed computing by its focus on large-scale resource sharing, innovative applications, and, in some cases, high-performance orientation. In this article, we define this new field. First, we review the "Grid problem," which we define as flexible, secure, coordinated resource sharing among dynamic collections of individuals, institutions, and resources-what we refer to as virtual organizations. In such settings, we encounter unique authentication, authorization, resource access, resource discovery, and other challenges. It is this class of problem that is addressed by Grid technologies. Next, we present an extensible and open Grid architecture, in which protocols, services, application programming interfaces, and software development kits are categorized according to their roles in enabling resource sharing. We describe requirements that we believe any such mechanisms must satisfy, and we discuss the central role played by the intergrid protocols that enable interoperability among different Grid systems. Finally, we discuss how Grid technologies relate to other contemporary technologies, including enterprise integration, application service provider, storage service provider, and peer-to-peer computing. We maintain that Grid concepts and technologies complement and have much to contribute to these other approaches.

The Anatomy of the Grid - Enabling Scalable Virtual Organizations

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.

An overview of AspectJ

Vehicular ad hoc networks using WLAN technology have recently received considerable attention. We present a position-based routing scheme called Connectivity-Aware Routing (CAR) designed specifically for inter-vehicle communication in a city and/or highway environment. A distinguishing property of CAR is the ability to not only locate positions of destinations but also to find connected paths between source and destination pairs. These paths are auto-adjusted on the fly, without a new discovery process. "Guards" help to track the current position of a destination, even if it traveled a substantial distance from its initially known location. For the evaluation of the CAR protocol we use realistic mobility traces obtained from a microscopic vehicular traffic simulator that is based on a model of driver behavior and the real road maps of Switzerland.

http://www.lst.ethz.ch/research/publications/INFOCOM_2007/INFOCOM_2007.pdf

Connectivity-Aware Routing (CAR) in Vehicular Ad-hoc Networks

Vehicular ad hoc networks (VANETs) using WLAN tech-nology have recently received considerable attention. The evaluation of VANET routing protocols often involves simulators since management and operation of a large number of real vehicular nodes is expensive. We study the behavior of routing protocols in VANETs by using mobility information obtained from a microscopic vehicular traffic simulator that is based on the on the real road maps of Switzerland. The performance of AODV and GPSR is significantly in uenced by the choice of mobility model, and we observe a significantly reduced packet delivery ratio when employing the realistic traffic simulator to control mobility of nodes. To address the performance limitations of communication pro-tocols in VANETs, we investigate two improvements that increase the packet delivery ratio and reduce the delay until the first packet arrives. The traces used in this study are available for public download.

/pdf/an-evaluation-of-inter-vehicle-ad-hoc-networks-based-on-mlpkp3tkjp.pdf

An evaluation of inter-vehicle ad hoc networks based on realistic vehicular traces

Control-Flow Integrity (CFI) is a defense which prevents control-flow hijacking attacks While recent research has shown that coarse-grained CFI does not stop attacks, fine-grained CFI is believed to be secure

We argue that assessing the effectiveness of practical CFI implementations is non-trivial and that common evaluation metrics fail to do so We then evaluate fullyprecise static CFI -- the most restrictive CFI policy that does not break functionality -- and reveal limitations in its security Using a generalization of non-control-data attacks which we call Control-Flow Bending (CFB), we show how an attacker can leverage a memory corruption vulnerability to achieve Turing-complete computation on memory using just calls to the standard library We use this attack technique to evaluate fully-precise static CFI on six real binaries and show that in five out of six cases, powerful attacks are still possible Our results suggest that CFI may not be a reliable defense against memory corruption vulnerabilities

We further evaluate shadow stacks in combination with CFI and find that their presence for security is necessary: deploying shadow stacks removes arbitrary code execution capabilities of attackers in three of six cases

/pdf/control-flow-bending-on-the-effectiveness-of-control-flow-2dtdhb3yz7.pdf

Control-flow bending: on the effectiveness of control-flow integrity

We present an on-the-fly mechanism that detects access conflicts in executions of multi-threaded Java programs. Access conflicts are a conservative approximation of data races. The checker tracks access information at the level of objects (object races) rather than at the level of individual variables. This viewpoint allows the checker to exploit specific properties of object-oriented programs for optimization by restricting dynamic checks to those objects that are identified by escape analysis as potentially shared. The checker has been implemented in collaboration with an "ahead-of-time"Java compiler. The combination fo static program analysis (escape-analysis) and inline instrumentation during code generation allows us to reduce the runtime overhead of detecting access conflicts. This overhead amounts to about 16-129% in time and less than 25% in space for typical benchmark applications and compares favorably to previously published on-the-fly mechanism that incurred an overhead of about a factor of 2-80 in time and up to a factor of 2 in space.

https://www.in.th-nuernberg.de/professors/praun/pubs/oopsla01.pdf

Object race detection

When using Aspect Oriented Programming in the development of software components, a developer must understand the program units actually changed by weaving, how they behave, and possibly correct the aspects used. Support for rapid AOP prototyping and debugging is therefore crucial in such situations. Rapid prototyping is difficult with current aspect weaving tools because they do not support dynamic changes. This paper describes PROSE (PROgrammable extenSions of sErvices), a platform based on Java which addresses dynamic AOP. Aspects are expressed in the same source language as the application (Java), and PROSE allows aspects to be woven, unwoven, or replaced at run-time.

https://www.lst.ethz.ch/research/publications/AOSD_2002/AOSD_2002.pdf

Thomas R. Gross

Papers

Connectivity-Aware Routing (CAR) in Vehicular Ad-hoc Networks

An evaluation of inter-vehicle ad hoc networks based on realistic vehicular traces

Control-flow bending: on the effectiveness of control-flow integrity

Object race detection

Dynamic weaving for aspect-oriented programming