HiTrust: building cross-organizational trust relationship based on a hybrid negotiation tree

Small-world phenomena have been observed in existing peer-to-peer (P2P) networks which has proved useful in the design of P2P file-sharing systems. Most studies of constructing small world behaviours on P2P are based on the concept of clustering peer nodes into groups, communities, or clusters. However, managing additional multilayer topology increases maintenance overhead, especially in highly dynamic environments. In this paper, we present Social-like P2P systems (Social-P2Ps) for object discovery by self-managing P2P topology with human tactics in social networks. In Social-P2Ps, queries are routed intelligently even with limited cached knowledge and node connections. Unlike community-based P2P file-sharing systems, we do not intend to create and maintain peer groups or communities consciously. In contrast, each node connects to other peer nodes with the same interests spontaneously by the result of daily searches

A model for inter-module analysis and optimizing compilation

Recent research into the implementation of logic programming languages has demonstrated that global program analysis can be used to speed up execution by an order of magnitude. However, currently such global program analysis requires the program to be analysed as a whole: sepárate compilation of modules is not supported. We describe and empirically evalúate a simple model for extending global program analysis to support sepárate compilation of modules. Importantly, our model supports context-sensitive program analysis and multi-variant specialization of procedures in the modules

Improving the compilation of prolog to C using moded types and determinism information

We describe the current status of and provide performance results for a prototype compiler of Prolog to C, ciaocc. ciaocc is novel in that it is designed to accept different kinds of high-level information, typically obtained via an automatic analysis of the initial Prolog program and expressed in a standardized language of assertions. This information is used to optimize the resulting C code, which is then processed by an off-the-shelf C compiler. The basic translation process essentially mimics the unfolding of a bytecode emulator with respect to the particular bytecode corresponding to the Prolog program. This is facilitated by a flexible design of the instructions and their lower-level components. This approach allows reusing a sizable amount of the machinery of the bytecode emulator: predicates already written in C, data definitions, memory management routines and áreas, etc., as well as mixing emulated bytecode with native code in a relatively straightforward way. We report on the performance of programs compiled by the current versión of the system, both with and without analysis information

Prokaryotic and Eukaryotic Community Structure in Field and Cultured Microbialites from the Alkaline Lake Alchichica (Mexico)

The geomicrobiology of crater lake microbialites remains largely unknown despite their evolutionary interest due to their resemblance to some Archaean analogs in the dominance of in situ carbonate precipitation over accretion. Here, we studied the diversity of archaea, bacteria and protists in microbialites of the alkaline Lake Alchichica from both field samples collected along a depth gradient (0–14 m depth) and long-term-maintained laboratory aquaria. Using small subunit (SSU) rRNA gene libraries and fingerprinting methods, we detected a wide diversity of bacteria and protists contrasting with a minor fraction of archaea. Oxygenic photosynthesizers were dominated by cyanobacteria, green algae and diatoms. Cyanobacterial diversity varied with depth, Oscillatoriales dominating shallow and intermediate microbialites and Pleurocapsales the deepest samples. The early-branching Gloeobacterales represented significant proportions in aquaria microbialites. Anoxygenic photosynthesizers were also diverse, comprising members of Alphaproteobacteria and Chloroflexi. Although photosynthetic microorganisms dominated in biomass, heterotrophic lineages were more diverse. We detected members of up to 21 bacterial phyla or candidate divisions, including lineages possibly involved in microbialite formation, such as sulfate-reducing Deltaproteobacteria but also Firmicutes and very diverse taxa likely able to degrade complex polymeric substances, such as Planctomycetales, Bacteroidetes and Verrucomicrobia. Heterotrophic eukaryotes were dominated by Fungi (including members of the basal Rozellida or Cryptomycota), Choanoflagellida, Nucleariida, Amoebozoa, Alveolata and Stramenopiles. The diversity and relative abundance of many eukaryotic lineages suggest an unforeseen role for protists in microbialite ecology. Many lineages from lake microbialites were successfully maintained in aquaria. Interestingly, the diversity detected in aquarium microbialites was higher than in field samples, possibly due to more stable and favorable laboratory conditions. The maintenance of highly diverse natural microbialites in laboratory aquaria holds promise to study the role of different metabolisms in the formation of these structures under controlled conditions

PP-trust-X: A system for privacy preserving trust negotiations

Trust negotiation is a promising approach for establishing trust in open systems, in which sensitive interactions may often occur between entities with no prior knowledge of each other. Although, to date several trust negotiation systems have been proposed, none of them fully address the problem of privacy preservation. Today, privacy is one of the major concerns of users when exchanging information through the Web and thus we believe that trust negotiation systems must effectively address privacy issues in order to be widely applicable. For these reasons, in this paper, we investigate privacy in the context of trust negotiations. We propose a set of privacy-preserving features for inclusion in any trust negotiation system, such as the support for the P3P standard, as well as a number of innovative features, such as a novel format for encoding digital credentials specifically designed for preserving privacy. Further, we present a variety of interoperable strategies to carry on the negotiation with the aim of improving both privacy and efficiency

The traust authorization Service

In recent years, trust negotiation has been proposed as a novel authorization solution for use in open-system environments, in which resources are shared across organizational boundaries. Researchers have shown that trust negotiation is indeed a viable solution for these environments by developing a number of policy languages and strategies for trust negotiation that have desirable theoretical properties. Further, existing protocols, such as TLS, have been altered to interact with prototype trust negotiation systems, thereby illustrating the utility of trust negotiation. Unfortunately, modifying existing protocols is often a time-consuming and bureaucratic process that can hinder the adoption of this promising technology. In this paper, we present Traust, a third-party authorization service that leverages the strengths of existing prototype trust negotiation systems. Traust acts as an authorization broker that issues access tokens for resources in an open system after entities use trust negotiation to satisfy the appropriate resource access policies. The Traust architecture was designed to allow Traust to be integrated either directly with newer trust-aware applications or indirectly with existing legacy applications; this flexibility paves the way for the incremental adoption of trust negotiation technologies without requiring widespread software or protocol upgrades. We discuss the design and implementation of Traust, the communication protocol used by the Traust system, and its performance. We also discuss our experiences using Traust to broker access to legacy resources, our proposal for a Traust-aware version of the GridFTP protocol, and Traust's resilience to attack. © 2008 ACM