Systems development approach: transcending methodology

Abstract.  This paper presents the findings of an empirical study investigating the nature of the process of information systems development. These findings are used to identify systems development approach, which extends understanding of the information systems development process beyond the levels of methodology and technical expertise. The term approach expresses the rich, varied, and complex ways in which professionals deal with development situations. The term transcends methodological components – which can be combined, tailored, or omitted altogether. Within approach, a framework for method choice, a key diagnostic scheme, and the use of a central repository reveal the significant background activity that goes into developing information systems. It is suggested that the information systems development process ultimately involves a professional using an approach to intervene in a problematic situation for developing the organization's information and, if needed, other systems. This understanding has implications for examining the field's ineffectiveness in relation to the approach adopted – rather than the methodology used.     

Towards social behavior in virtual-agent navigation

We present Social Groups and Navigation (SGN), a method to simulate the walking behavior of small pedestrian groups in virtual environments. SGN is the first method to simulate group behavior on both global and local levels of an underlying planning hierarchy. We define quantitative metrics to measure the coherence and the sociality of a group based on existing empirical data of real crowds. SGN does not explicitly model coherent and social formations, but it lets such formations emerge from simple geometric rules. In addition to a previous version, SGN also handles group-splitting to smaller groups throughout navigation as well as social sub-group behavior whenever a group has to temporarily split up to re-establish its coherence. For groups of four, SGN generates between 13% and 53% more socially-friendly behavior than previous methods, measured over the lifetime of a group in the simulation. For groups of three, the gain is between 15% and 31%, and for groups of two, the gain is between 1% and 4%. SGN is designed in a flexible way, and it can be integrated into any crowd-simulation framework that handles global path planning and any path following as separate steps. Experiments show that SGN enables the simulation of thousands of agents in real time.     

Efficient In-Situ Regeneration Method of the Catalytic Activity of Aged TWC

The expansion of durability of deactivated “three-way” catalysts (TWCs) used in gasoline-driven cars by applying efficient, economically viable and environmentally friendly methods for the in␣situ regeneration of their performance to acceptable levels was investigated. New experimental results on the use of a weak oxalic acid washing solution as a means of an efficient regeneration method of a severely aged (83,000 km mileage) commercial TWC are presented. Oxalic acid is shown to be the most efficient extracting agent of phosphorus, a severe poison of TWCs, among acetic acid, citric acid, NTA and EDTA investigated. X-ray diffraction studies provided strong evidence that washing of the aged TWC results in the removal of CePO₄, AlPO₄ and (Mg,Ca,Zn)₃(PO₄)₂ type phosphates leading to a significant increase of BET area and pore volume, as well as of CO and NO conversions (catalytic activity tests). The latter is strongly related with the increase in the number of active catalytic sites, as illustrated by in␣situ DRIFTS studies, after opening closed pores and uncovering additional catalyst surface.     

Randomized Instruction Sets and Runtime Environments Past Research and Future Directions

The author describes past research and future directions on instruction set randomization (ISR), a general technique for protecting against code-injection attacks. Such attacks are commonly encountered in a variety of application domains, remotely targeting program binaries, Web application and database backends, and Web browsers. Collectively, they represent the vast majority of reported attacks in bug- and incident-tracking repositories for the past decade, with no sign of abatement. ISR provides for a separation of code from data by randomizing the execution environment of legitimate code, which has to be suitably transformed using a key shared with the execution environment. This article describes the motivation behind ISR, the high-level concept, its use in two different application domains (binary code injection and SQL injection attacks), the author's findings and experiences (including several limitations, both of the technique and of prototypes), and future directions for improvements and application of ISR. Although he tries to provide broad coverage of the topic, the primary focus is on the research conducted at the Network Security Laboratory at Columbia.     

A Cross Layer Scheduling Framework for Supporting Bursty Data Applications in WCDMA Networks

In future wireless networks multimedia applications are expected to finally dominate the overall traffic volume. Shared channels are more suitable for the transmission of this type of traffic, as they are able to periodically adjust their transmission rate. In this paper, we introduce a cross-layer framework for WCDMA based networks which aims to make the packet scheduling procedure more efficient. In addition to that, we further propose a traffic scheduling scheme which serves the connections not only according to their delay sensitivity, but also according to the predicted state of their wireless channel. The efficiency of the proposed scheme, in terms of average packet delay and channel utilization is verified via simulations.     

Capability-Based Defenses Against DoS Attacks in Multi-path MANET Communications

We present the design, implementation, and evaluation of CapMan, a capability-based security mechanism that prevents denial-of-service (DoS) attacks against mobile ad-hoc networks (MANETs). In particular, our approach is designed to mitigate insider attacks that exploit multi-path routing to flood with packets on other participating nodes in the network. CapMan is instantiated on every node and enforces capability limits that effectively regulate the traffic for all end-to-end network flows. Each capability is issued and advertised by the capability distribution module, and is globally maintained via the capability enforcement logic. By periodically exchanging small usage summaries, all cooperating nodes are informed of the global network state in a scalable and consistent manner. The distribution of summaries empowers individual nodes to make informed decisions and regulate traffic as dictated by the per-flow capabilities across multiple dynamic routing paths. We implemented a prototype of CapMan as a module of the NS2 simulator. We conducted extensive simulations with the prototype using AOMDV as the underlying multi-path routing protocol. Both theoretical analysis and experimental results validate that our mechanism can effectively curtail sophisticated DoS attacks that target multi-path routing in MANETs. We can protect the overall network health even when both the initiator and the responder are malicious insiders and collude in an attempt to deprive the network of valuable resources. Finally, our results show that CapMan introduces relatively small and configurable network overhead and imposes minimal impact on non-attacking traffic flows.     

Layer‐By‐Layer Electropeeling of Organic Conducting Material Imaged In Real Time

Soft materials comprising low‐molecular‐weight organic molecules are attracting increasing interest because of their importance in the development of a number of emerging areas in nanoscience and technology, including molecular electronics, nanosystems for energy conversion, and devices in the widest sense. Their interaction with electrodes and their behavior under electric fields is a topic of vital significance for these areas, and about which very little is known. Here unprecedented evidence is presented for the controlled peeling of organic molecular material when a voltage is applied between the conducting system and the conducting probe of a scanning force microscope. The rate of removal of the material from the surface of the bulk conducting supramolecular material can be tuned. It depends on the potential applied and is initiated only above a threshold value of 200 mV. The results indicate the importance of electric fields on the stability and performance of conducting organic systems at the nanoscale.