Capturing and Using the Operational Semantics of Large Distributed Systems: Sharing Common Application Requirements in Virtual Organisations

The aim of the paper is to discuss the rising potential of social software to increase the knowledge management capabilities of virtual product development teams. It presents six fundamental transitions, elaborated from the empirical findings, which justify the rise of a more bottom-up, social creation and sharing of engineering knowledge in the virtual organisation. The study suggests that traditional engineering knowledge management approaches alone are not sufficient to support development activities in the virtual organisation, and that such teams display an increasing demand for social, comparatively lightweight and remixable platforms for bottom-up, social creation and sharing of knowledge.

Today we are witnessing the necessity to align Business and Information Technology (IT) as well as a change in the role of IT from an enabler to an industrial sector in its own right. Based on the assumption that businesses in different sectors of the economy will require IT for different reasons and in different ways, this article introduces the EU project plugIT that aspires to develop an IT-Socket that will realize the vision of businesses "plugging-in" to IT. Three demonstration scenarios deal with: (1) "Certification" of IT infrastructure to stay compliant with regulations, (2) "Virtual Organisation" by evolving the current service orientation to a higher and more business driven abstraction as well as, (3) "Governance" of IT infrastructure introducing business context into highly distributed and complex systems. The IT-Socket follows a model-driven approach by introducing graphical modelling languages as mediators between the domain experts and IT. The research challenge is to link human interpretable graphical models – partly semi-formal – with machine interpretable semantic formalisms to enable: (1) a tighter involvement of domain experts when expressing formal knowledge specifying business requirements on IT infrastructure and services, (2) different graphical modelling languages for different views on the IT-Socket to provide modelling languages the domain expert is used to work with as well as, (3) a domain specific notation for semantics by integrating formal concepts of semantics with the graphic notation from modelling languages.

Distributed Denial-of-Service (DDoS) attacks towards name servers of the Domain Name System (DNS) have threaten to disrupt this critical service. This paper studies the vulnerability of the cache server to the flooding DNS query traffic. As the resolution service provided by cache server, the incoming DNS requests, even the massive attacking traffic, are maintained in the waiting queue. The sojourn of requests lasts until the corresponding responses are returned from the authoritative server or time out. The victim cache server is thus overloaded by the pounding traffic and thereafter goes down. The impact of such attacks is analyzed via the model of queuing process in both cache server and authoritative server. Some specific limits hold for this practical dual queuing process, such as the limited sojourn time in the queue of cache server and the independence of the two queuing processes. The analytical results are presented to evaluate the impact of DDoS attacks on cache server. Finally, numerical results are provided for further analysis.

A distributed system such as a grid infrastructure consists of different institutions and organizations that, with the goal of sharing resources with each other, need to establish trust relationships and security policies. Most implemented systems make use of the PKI-compliant grid security infrastructure (GSI) for authentication purposes and use different authorization methods that rely on users' membership in the grid logical domain (the virtual organization). However, each grid site hosting a resource provider needs to set its own admission policies for decentralized management. Focusing on web grid resources, the paper describes security mechanisms acting at global network, VO and target site levels. This papers provides a method based on the Java handlers ' technique available for a resource provider at a target grid site to secure its web resources. Moreover, the paper proposes the future use of an integration system between a VO-based system and federated identity-based infrastructure.

In this paper, the problem of robust stabilization of a wheeled vehicle is addressed. The configuration (position and orientation) set of the vehicle is divided into two parts: global and local configuration sets. The novelty of this paper is the design of a hybrid feedback controller that assigns different objectives in the vehicle’s global and local behaviors. Two Lyapunov functions for individual objectives are introduced that allow a hybrid feedback control law to pursue different objectives. In the global sense, it is important to reach the target point as quickly as possible, but once the vehicle reaches is near the goal, a precise maneuvering by rejecting disturbances including tire slippage and measurement noise becomes important. The asymptotical stability and robustness of the closed loop system are assured. The derived control law is validated by simulations and experiments using an autonomous forklift.

Web services as a new distributed system technology have been widely adopted by industries in the areas, such as enterprise application integration (EAI), business process management (BPM), and virtual organization (VO). However, lack of semantics in the current Web service standards has become a major barrier in service discovery and composition. To tackle the semantic issues of Web services, this paper proposes a comprehensive semantic service description framework – CbSSDF and a two-step service discovery mechanism based on CbSSDF—to help service users to easily locate their required services. The authors give a detailed explanation of CbSSDF, and then evaluate the framework by comparing it with OWL-S to examine how the proposed framework can improve the efficiency and effectiveness of service discovery and composition. The evaluation is carried out by analysing the different proposed solutions based on these two frameworks for achieving a series of tasks in a scenario.

The Domain Name System (DNS) is an essential service for the Internet which maps host names to IP addresses. The DNS Root Sever System operates the top of this namespace. RIPE Atlas observes DNS from more than 11k vantage points (VPs) around the world, reporting the reliability of the DNS Root Server System in DNSmon. DNSmon shows that loss rates for queries to the DNS Root are nearly 10% for IPv6, much higher than the approximately 2% loss seen for IPv4. Although IPv6 is "new," as an operational protocol available to a third of Internet users, it ought to be just as reliable as IPv4. We examine this difference at a finer granularity by investigating loss at individual VPs. We confirm that specific VPs are the source of this difference and identify two root causes: VP islands with routing problems at the edge which leave them unable to access IPv6 outside their LAN, and VP peninsulas which indicate routing problems in the core of the network. These problems account for most of the loss and nearly all of the difference between IPv4 and IPv6 query loss rates. Islands account for most of the loss (half of IPv4 failures and 5/6ths of IPv6 failures), and we suggest these measurement devices should be filtered out to get a more accurate picture of loss rates. Peninsulas account for the main differences between root identifiers, suggesting routing disagreements root operators need to address. We believe that filtering out both of these known problems provides a better measure of underlying network anomalies and loss and will result in more actionable alerts.

Extending indigenous knowledge to unveil the evolutionary journey of food preferences and socio-cultural phenomena

The main scope of this dissertation has been to give a contribution to the evaluation of seismic performance of CFS structures and in particular of diagonal strap braced walls. To this end, two main objectives are pursued in this work: the study of the seismic behaviour of diagonal strap braced walls in terms of global response and the study of local behaviour of connections to understand their influence on the global seismic behaviour of walls. In the context of ReLUIS-DPC project, a wide experimental program was planned and carried out. It consists of full-scale experimental tests on walls to investigate the global behaviour and small-scale experimental tests on materials, simple mechanical joints and connections to investigate the influence of the local behaviour on the global seismic behaviour. The experimental tests have been performed at the Dist Laboratory (Department of Structures for Engineering and Architecture, Naples), of the University of Naples Federico II. The obtained results demonstrate a satisfactory experimental response in terms of stiffness, strength and deformation capacity, largely confirming the theoretical predictions. Since the final scope of the whole study, and in particular of the experimental campaign, is to provide appropriate design criteria for diagonal strap braced CFS structures to be introduced in Italian seismic code, considerations about design criteria were presented, on the basis of the design assumptions and the experimental test results, in comparison with the prescriptions of national and international seismic codes. The attention is focused on the behaviour factor, the diagonal brace verifications and the overstrength of fragile elements.

A widely adopted method of strengthening existing reinforced concrete (RC) structures, especially for marine concrete structures, is to use external bonded fiber-reinforced polymer (FRP). However, although numerous studies in this field have been reported, accurate simulation of localized material behaviors such as crack opening and interfacial sliding remains challenging. Compared to other simulation methods, mesoscale models offer the promise of capturing these complexities. Nevertheless, there has been very little application of mesoscale simulations in analysis of FRP-strengthened RC structures due to a lack of relevant constitutive models. To fill this gap, the authors have recently developed local bond models for the FRP-concrete interface in the three-dimensional rigid body spring model (3D RBSM). The model’s parameters are defined with easily interpretable physical implications and straightforward computational methods. In this work, this mesoscale model is extended and applied to simulate the flexural behavior of FRP-strengthened RC beams. The simulation results closely align with experiments in both global and local behaviors. The parametric study conducted in this work highlights the critical role of interfacial normal bond strength between FRP and concrete in dictating flexural behavior. The capability of 3D RBSM in simulating the strain distribution along the FRP and capturing intricate localized behaviors aligned with flexural and shear forces is demonstrated. Overall, this paper reinforces the potential of 3D RBSM as a robust tool for analyzing the complex behaviors of FRP-strengthened concrete structures.

Replication of information among multiple Web servers is necessary to support high request rates to popular Web sires. A clustered Web-server organization is preferable to multiple independent mirrored-servers because it maintains a single interface to the users and has the potential to be more scalable, fault-tolerant and better load balanced. In this paper we propose a Web cluster architecture in which the Domain Name System sen er (DNS), that dispatches the user requests among the servers through the URL-name to IP-address mapping mechanism, is integrated with a redirection request mechanism based on the HTTP protocol. This should alleviate the side effect of caching the IP-address mapping at intermediate name servers. We compare many alternative mechanisms, including synchronous vs asynchronous activation, and centralized vs distributed decision on redirection. Moreover, we analyze reassignment of entire domains or individual client requests, different types of status information, and different sen er selection policies for redirecting requests. Our results show that the combination of centralized and distributed dispatching policies allows the Web-server cluster to handle the high loan skews in the WWW environment.

Online information security is a major concern for both users and companies, since data transferred via the Internet is becoming increasingly sensitive. The World Wide Web uses Hypertext Transfer Protocol (HTTP) to transfer information and Secure Sockets Layer (SSL) to secure the connection between clients and servers. However, Hypertext Transfer Protocol Secure (HTTPS) is vulnerable to attacks that threaten the privacy of information sent between clients and servers. In this paper, we propose Enc-DNS-HTTP for securing client requests, protecting server responses, and withstanding HTTPS attacks. Enc-DNS-HTTP is based on the distribution of a web server public key, which is transferred via a secure communication between client and a Domain Name System (DNS) server. This key is used to encrypt client-server communication. The scheme is implemented in the C programming language and tested on a Linux platform. In comparison with Apache HTTPS, this scheme is shown to have more effective resistance to attacks and improved performance since it does not involve a high number of time-consuming operations.

Chapter 4 - MCSA/MCSE 70-291: NetBIOS Name Resolution and WINS

Information Centric Networks (ICN) has emerged as a new Internet paradigm where the users are being provided seamless access to contents rather than the host as in classical approach. For ICN realization, the current Internet requires architectural changes. These changes must be incorporated such that existing applications continue running without any difficulties. In this paper, we introduce a novel ICN architecture, called Overlay Information Centric Networks (O-ICN), which separates the data plane from the control plane activities of the network. Unlike the usual ICN architectures, in our approach naming and routing (control plane) functionalities have been segregated from the caching (data plane) functionality at each ICN router. We introduce a new module called an ICN Manager which is an extended version of Domain Name System (DNS) server and performs name resolution along with routing functionalities for ICN type of requests as well as the normal DNS resolution for non-ICN type of requests. The O-ICN architecture can be deployed incrementally over the current Internet and can operate both as ICN and non-ICN/legacy network simultaneously. This can also be implemented both in Software Defined Networks (SDN) as well as non-SDN networks without much modifications. The proposed architecture provides benefits in terms of simplification of network management, vendor independent solution, better use of network resources in terms of bandwidth and delay, and reduction of deployment/operational cost of the network.

We recall Interaction Systems for verifying the achievement of goals (requirements) in distributes systems by adequately representing constraints and influences between the system parts. Patterns of local and global behaviour are induced by local restrictions or excitements. We demonstrate in a stepwise manner the achievement of global goals using an approximation by local ones. The resulting interaction system may be regarded as a sufficiently realistic specification of a distributed system.