18614429
A petri net based XML firewall security model for web services invocation
An XML firewall differs from a conventional firewall because its major task is to control access to web services rather than to filter untrusted addresses. An XML firewall can effectively protect web services from being attacked by inspecting a complete XML message including its head and data segments, and rejecting unauthorized web services invocation. In this paper, we propose a formal XML firewall security model using role-based access control (RBAC). Our proposed model supports user authentication and user authorization according to information stored in a user database and a policy database associated with an XML firewall. The formal model is designed compositionally using Petri nets, which can serve as a high-level design for XML firewall implementation. The key components of our compositional security model are the application model and the XML firewall model. To illustrate the advantages of our formal approach, we use an existing Petri net tool to verify some key properties of our model, such as boundedness and liveness.
5913002
Formal modeling of synchronization methods for concurrent objects in Ada 95
One important role for Ada programming is to aid engineering of concurrent and distributed software. In a concurrent and distributed environment, objects may execute concurrently and need to be synchronized to serve a common goal. Three basic methods by which objects in a concurrent environment can be constructed and synchronized have been identified [1]. To formalize the semantics of these methods and to provide a formal model of their core behavior, we provide some graphic models based on the Petri net formalism. The purpose of this formal modeling is to illustrate the possibility of automatic program analysis for object-oriented features in Ada-95. Models for the three distributed- object synchronization methods are discussed, and a potential deadlock situation for one of the methods/models is illustrated. We conclude with some comparison of the three methods in terms of the model abstractions.
15831559
An agent-based Petri net model with application to seller/buyer design in electronic commerce
Agents are becoming one of the most important topics in distributed and autonomous decentralized systems (ADS), and there are increasing attempts to use agent technologies to develop software systems in electronic commerce. Such systems are complex and there is a pressing need for system modeling techniques to support reliable, maintainable and extensible design. G-Nets are a type of Petri net defined to support modeling of a system as a set of independent and loosely-coupled modules. The authors first introduce an extension of G-Net, agent based G-Net, as a generic model for agent design. Then new communication mechanisms are introduced to support asynchronous message passing among agents. To illustrate that our formal modeling technique is effective for agent modeling in electronic commerce, a price-negotiation protocol example between buyers and sellers is provided. Finally, by analyzing an ordinary Petri net reduced from our agent based G-Net models, we conclude that our agent based G-Net models are L3-live, concurrent and effective for agent communications.
955272
A Formal Approach to Detecting Shilling Behaviors in Concurrent Online Auctions
Shilling behaviors are one of the most serious fraud problems in online auctions, which make winning bidders have to pay more than what they should pay for auctioned items. In concurrent online auctions, where multiple auctions for the same type of items are running simultaneously, shilling behaviors can be even more severe because detecting, predicting and preventing such fraudulent behaviors become very difficult. In this paper, we propose a formal approach to detecting shilling behaviors in concurrent online auctions using model checking techniques. We first develop a model template that represents two concurrent online auctions in Promela. Based on the model template, we derive an auction model that simulates the bidding processes of two concurrent auctions. Then we use the SPIN model checker to formally verify if the auction model satisfies any questionable behavioral properties that are written in LTL (Linear Temporal Logic) formulas. Thus, our approach simplifies the problem of searching for shilling behaviors in concurrent online auctions into a model checking problem. Finally, we provide a case study to illustrate how our approach can effectively detect possible shill bidders.
205925700
Compositional Petri net models of advanced tasking in Ada-95
The Ada language has been designed to support development of concurrent and distributed software. While the Ada-83 standard defined the basic mechanisms of rendezvous-based tasking, the Ada-95 standard significantly extended this capability with the introduction of several advanced tasking constructs. We present and discuss formal models of these key tasking constructs using the Petri net model. We also provide some formal evaluation of the models using one particular net-based method, invariant analysis. The constructs considered are the asynchronous transfer of control, the protected object, and the requeue statement. By modeling these advanced Ada tasking constructs with Petri nets, we obtain compositional models of the constructs that are complementary to earlier work in net-based modeling of Ada tasking, both in terms of defining precise behavior for tasking semantics, and also in terms of providing support for automated analysis of concurrent software.
9774737
A framework for modeling agent-oriented software
With the increasing importance of complex software systems in the software industry, the need for using agent technologies to develop large-scale commercial and industrial software systems is growing rapidly. Such systems are complex, and there is a pressing need for system modeling techniques to support reliable, maintainable and extensible design. G-nets are a type of Petri net defined to support the modeling of a system as a set of independent and loosely-coupled modules. In this paper, we first introduce an extension of G-nets - the agent-based G-net - as a generic model for agent design. Then, to progress from an agent-based design model to an agent-oriented model, new mechanisms to support inheritance modeling are introduced. To illustrate our formal modeling technique for multi-agent systems, an example of an agent family in electronic commerce is provided.
15979413
Consumers' Privacy Concerns toward Using Location-Based Services: An Exploratory Framework and Research Proposal
Privacy concerns associated with the use of Location-Based Services (LBS) may ultimately prevent consumers from gaining the ‘anytime anywhere’ convenience. Through a psychological control lens, we examine whether individual difference variables such as locus of control (LOC) could have moderating effects on the relationship between privacy concern and three privacy assurance mechanisms in the LBS context. The paper develops a preliminary research model which conceptualizes the moderating effects of LOC by extending Xu and Teo (2004)’s research model. With an explicit focus on LOC, this study will not only add an important piece of information to our understanding of consumers’ reactions to LBS but also can help frame the ongoing policy and scholarly debate surrounding the relative effectiveness of technology, industry self-regulation and government legislation in ensuring consumers’ privacy. We believe that our findings will be able to offer practical implications for the various players in the LBS landscape: merchants, wireless service providers, wireless device manufacturer, privacy advocates and legislators.
10887257
Foundations of SMS commerce success: lessons from SMS messaging and co-opetition
As a convenient and low-cost mobile communication technology, short messaging service (SMS) is experiencing very rapid growth. It is reported that 700 million mobile phone users worldwide sent 20 to 30 billion SMS messages every month in 2001. At the same time, SMS commerce applications have emerged to provide mobile users consumer-oriented services. The huge SMS messaging customer base serves as the potential SMS commerce customer base according to K. Kellett and A. Linde (2001) . However, the bloom in messaging business does not automatically lead to the success of general SMS commerce applications. In this paper, we analyzed SMS developments in three different countries to derive three success indicators for SMS messaging and relate them to the success of SMS commerce. Based on the proposed SMS application framework, we postulate four additional hypothesized success factors that could uniquely contribute to the success of SMS commerce. Our findings provide practical implications for promoting SMS commerce applications successfully.
5903660
Stylized rendering of 3D scanned real world environments
This paper presents an interactive non-photorealistic rendering (NPR) system that stylizes and renders outdoor scenes captured by 3D laser scanning. In order to deal with the large size, complexity and inherent incompleteness of data obtained from outdoor scans, our system represents outdoor scenes using points instead of traditional polygons. Algorithms are then developed to extract, stylize and render features from this point representation. In addition to conveying various NPR styles, our system also promises consistency in animation by maintaining stroke coherence and density. We achieve NPR of large data at interactive rates by designing novel data structures and algorithms as well as leveraging new features of commodity graphics hardware.
10910603
Hybrid Forward Resampling and Volume Rendering
The transforming and rendering of discrete objects, such as traditional images (with or without depths) and volumes, can be considered as resampling problem – objects are reconstructed, transformed, filtered, and finally sampled on the screen grids. In resampling practices, discrete samples (pixels, voxels) can be considered either as infinitesimal sample points (simply called points) or samples of a certain size (splats). Resampling can also be done either forwards or backwards in either the source domain or the target domain. In this paper, we present a framework that features hybrid forward resampling for discrete rendering. Specifically, we apply this framework to enhance volumetric splatting. In this approach, minified voxels are taken simply as points filtered in screen space; while magnified voxels are taken as spherical splats. In addition, we develop two techniques for performing accurate and efficient perspective splatting. The first one is to efficiently compute the 2D elliptical geometry of perspectively projected splats; the second one is to achieve accurate perspective reconstruction filter. The results of our experiments demonstrate both the effectiveness of antialiasing and the efficiency of rendering using this
7143460
A system of high-dimensional, efficient, long-cycle and portable uniform random number generators
We propose a system of multiple recursive generators of modulus <i>p</i> and order <i>k</i> where all nonzero coefficients of the recurrence are equal. The advantage of this property is that a single multiplication is needed to compute the recurrence, so the generator would run faster than the general case. For <i>p</i> = 2<sup>31</sup> − 1, the most popular modulus used, we provide tables of specific parameter values yielding maximum period for recurrence of order <i>k</i> = 102 and 120. For <i>p</i> = 2<sup>31</sup> − 55719 and <i>k</i> = 1511, we have found generators with a period length approximately 10<sup>14100.5</sup>.