Abstract It is one of the most important challenges to balance between security and scalability in large distributed data systems. In this paper, we introduce a new data distribution model, which is a generalized tree structure called as multitree. And its access control strategy is investigated. In our multitree data model, the database schema is expressed as a schema graph, and... It is one of the most important challenges to balance between security and scalability in large distributed data systems. In this paper, we introduce a new data distribution model, which is a generalized tree structure called as multitree. And its access control strategy is investigated. In our multitree data model, the database schema is expressed as a schema graph, and a database instance is imagined as a data graph. It is different from the traditional hierarchical data model, since a node in our multitree model can have many parent nodes. All the data graphs or schema are transformed into multitrees. The complex data relation of the distributed data systems is reduced based on graph theory. The complexity of distribution is decreased significantly. In the multitree model, each user has a maximum access range corresponding to its multitree. It is integrated naturally with security. We use organization structure to bound the data range that a user can access, and use roles to restrict the operations that the user can perform. The scalability of data distribution and access control adminstration are evaluated through the instance adapted from the TPC-C database. The results illustrates our data distribution model is helpful for the system to be resilient and scalable. It is suitable for large distributed system and cloud relational database. Read More Read Less

Abstract In practice, we usually require a key agreement protocol to establish a common secret key for enciphering/deciphering messages. Now, most protocols can establish n2 common secret keys in a single round of messages exchange. In this paper, we shall propose an extended protocol to establish 2n2 common secret keys in a single round. The proposed protocol is based on bilinear... In practice, we usually require a key agreement protocol to establish a common secret key for enciphering/deciphering messages. Now, most protocols can establish n2 common secret keys in a single round of messages exchange. In this paper, we shall propose an extended protocol to establish 2n2 common secret keys in a single round. The proposed protocol is based on bilinear pairings. Moreover, the correctness, security, and efficiency of our proposed protocol are presented. Read More Read Less

Abstract In order to provide quality delivery to delay sensitive applications such as voice and video, it is extremely important that mobile Ad Hoc networks provide quality of service (QoS) support in terms of bandwidth and delay. Most existing routing protocols for mobile Ad Hoc networks (MANETs) are designed to search for the shortest path with minimum hop counts. However, the... In order to provide quality delivery to delay sensitive applications such as voice and video, it is extremely important that mobile Ad Hoc networks provide quality of service (QoS) support in terms of bandwidth and delay. Most existing routing protocols for mobile Ad Hoc networks (MANETs) are designed to search for the shortest path with minimum hop counts. However, the shortest routes do not always provide the best performance, especially when there are congested nodes along these routes. In this paper, we propose an on demand delay based quality of service routing protocol (AODV-D) to ensure that delay does not exceed a maximum value. First in this paper, we compare the performance of two prominent on demand routing protocols AODV and DSR in stressful situation. As the performance of AODV has been found better in our simulation than DSR, we decided to modify AODV routing protocol to provide quality-of-service. This protocol takes into consideration MAC layer channel contention information and number of packets in the interface queue in addition to minimum hops. The protocol is implemented and simulated using GlomoSim simulator. Performance comparisons of the proposed AODV-D protocol against AODV, and QoS-AODV is presented and shown that the proposed protocol outperforms existing ones. Read More Read Less

Abstract In this paper, we investigate on potential improvements to Information Retrieval (IR) models related to document representation and conceptual, topic retrieval, in medical document collections. We propose the TSRM1 (Term Similarity and Retrieval Model) approach, where document representations are based on multi-word domain terms, rather than mere single key-words, typically applied in traditional IR. The proposed representation is semantically compact... In this paper, we investigate on potential improvements to Information Retrieval (IR) models related to document representation and conceptual, topic retrieval, in medical document collections. We propose the TSRM1 (Term Similarity and Retrieval Model) approach, where document representations are based on multi-word domain terms, rather than mere single key-words, typically applied in traditional IR. The proposed representation is semantically compact and more efficient, being reduced to a limited number of meaningful multi-word terms (phrases), rather than large vectors of single-words, part of which may be void of distinctive content semantics. In computing document similarity, contrary to other state-of-the-art methods examined in this work, TSRM adopts a knowledge poor solution, namely an approach which does not require any existing knowledge resources, such as ontologies, or thesauri. The evaluation of TSRM is based on OHSUMED, a standard TREC collection of medical documents and illustrated the efficiency of TSRM over other well established general purpose IR models. Read More Read Less

Abstract Learning by discussion when applied to on-line collaborative learning settings can provide significant benefits for students in education in general. Indeed, the discussion process plays an important social task in collaborative learning practices. Participants can discuss about the activity being performed, collaborate with each other through the exchange of ideas that may arise, propose new resolution mechanisms, justify and refine... Learning by discussion when applied to on-line collaborative learning settings can provide significant benefits for students in education in general. Indeed, the discussion process plays an important social task in collaborative learning practices. Participants can discuss about the activity being performed, collaborate with each other through the exchange of ideas that may arise, propose new resolution mechanisms, justify and refine their own contributions, and as a result, acquire new knowledge. Considering these benefits, current educational organizations incorporate on-line discussions into web-based courses as part of the very rationale of their pedagogical models. However, in-class collaborative assignments are usually greatly participated and contributed, which makes the monitoring and assessment tasks by tutors and moderators time-consuming, tedious and error-prone. Specially hard if not impossible by human tutors is to manually deal with the sequences of hundreds of contributions making up the discussion threads and the relations between these contributions. Consequently, tutoring tasks during on-line discussions usually restrict to offer evaluation results of the contributing effort and quality after the collaborative learning activity takes place and thus neglect the essential issue of constantly considering the process of knowledge building while it is still being performed. In this paper, we propose a multidimensional model based on data analysis from online collaborative discussion interactions that provides a first step towards an automatic evaluation in just-in-time fashion. The context of this study is a real on-line discussion experience that took place at the Open University of Catalonia. Read More Read Less

Abstract Website Information Architecture (IA) is primarily treated as a new discipline that is concerned with design principles and architecture of information in digital landscape. Proliferation of revolutionary models for interdisciplinary applications of IA, however lack theoretical perspectives, empirical evidence and cultural context. Here, we proposed a new model called Web Architectural-Inducing Model (WA-IM). The model was developed based from existing... Website Information Architecture (IA) is primarily treated as a new discipline that is concerned with design principles and architecture of information in digital landscape. Proliferation of revolutionary models for interdisciplinary applications of IA, however lack theoretical perspectives, empirical evidence and cultural context. Here, we proposed a new model called Web Architectural-Inducing Model (WA-IM). The model was developed based from existing literature and available architectural proposition from prior work. We tested the model suggesting that website IA being conceptualized as multidimensional constructs by exploring the applicability of WA-IM to web localization process from a socio-cognitive cultural perspective. The research methodology involves a web-based survey on Muslim online user as the cultural case study where 427 usable international responses were accumulated. The construct validation of the multifactor structure of website IA was assessed via confirmatory factor analysis (CFA) by using structural equation modeling. AMOS 7.0 was used to evaluate the five factor hypothesis goodness fit model. The result revealed that website IA is indeed a multidimensional construct composed of five factors: content-information, content-trust, navigation-traits, navigation-wayfindings and context. We conclude our study by providing empirical evidence for WA-IM in a form of goodness-fit-structure as part of the localization process towards the creation of cultural information structure. Read More Read Less

Abstract The effort to rigorously modeling critical systems is becoming more and more common. However, we see also other systems that come into account, i.e. systems of independently developed systems. In this paper, we offer a new approach to modeling of a system. We show that a state (from an outer point of view) can be regarded as a capability of... The effort to rigorously modeling critical systems is becoming more and more common. However, we see also other systems that come into account, i.e. systems of independently developed systems. In this paper, we offer a new approach to modeling of a system. We show that a state (from an outer point of view) can be regarded as a capability of the system to participate in interactions with the environment. Furthermore, we describe the capability by a mathematical object and discuss strictness of this description. Finally, we define a simple calculus over capabilities and show that capabilities of the system are a solution of a system of equations in the calculus. Read More Read Less