37556055
A Metadata Tool for Retrieval from Heterogeneous Distributed XML Documents
A metadata approach for retrieval from heterogeneous distributed XMLdo cuments is given. A prototype system uses distributed metadata to generate a GUI data integration tool, for describing mappings between master and local DTDs, by assigning index numbers and specifying conversion functions. A DDXMI (Distributed Document XML Metadata Interchange) file is generated based on the mappings, and used to translate queries over the virtual master document into sub-queries to local documents. Quilt is the XMLq uery language. An experiment testing feasibility is reported using three bibliography documents. The system runs under NT, using Java servelets and JavaCC.
12571017
A Metadata Integration Assistant Generator for Heterogeneous Distributed Databases
This paper describes a metadata interchange approach for semi-automatedin tegration of heterogeneous distributedd atabases. Our system prototype uses distributed metadata to generate a GUI tool for a meta-user (who does the metadata integration) to describe mappings between master and source databases by assigning index number and specifying conversion function names; the system uses Quilt as its XML query language. The queries for the local databases being transparent for users are generated, which is based on the metadata built semi-automatically. An experiment testing feasibility is reportedin which 3 different publishers' databases are integrated.
40285763
Critical Points for Interactive Schema Matching
Experience suggests that fully automated schema matching is infeasible, especially for n-to-m matches involving semantic functions. It is therefore advisable for a matching algorithm not only to do as much as possible automatically, but also to accurately identify the critical points where user input is maximally useful. Our matching algorithm combines several existing approaches, with a new emphasis on using the context provided by the way elements are embedded in paths. A prototype tested on biological data (gene sequence, DNA, RNA, etc.) and on bibliographic data, shows significant performance improvements from user feedback and context checking. In non-interactive mode on the purchase order schemas, it compares favorably with COMA, the most mature schema matching system in literature, and also correctly identifies critical points for user input.
7098845
Security Analysis of Several Group Signature Schemes
At Eurocrypt’91, Chaum and van Heyst introduced the concept of group signature. In such a scheme, each group member is allowed to sign messages on behalf of a group anonymously. However, in case of later disputes, a designated group manager can open a group signature and identify the signer. In recent years, researchers have proposed a number of new group signature schemes and improvements with different levels of security. In this paper, we present a security analysis of several group signature schemes proposed in [25, 27, 18, 31]. By using the same method, we successfully identify several universally forging attacks on these schemes. In our attacks, anyone (not necessarily a group member) can forge valid group signatures on any messages such that the forged signatures cannot be opened by the group manager. We also discuss the linkability of these schemes, and further explain why and how we find the attacks.
17122000
Efficient and robust key management for large mobile ad hoc networks
Existing research efforts in key management can only handle very limited number of nodes and are vulnerable to active attacks. In addition, the flexibility and adaptivity of handling dynamic risks in different parts of networks, although critical in the practical usages of ad hoc networks, have been largely ignored. In this paper, we propose a novel hierarchical scheme based on threshold cryptography to address both security and efficiency issues of key management and certification service in Mobile Ad hoc Network (MANET). The main contributions of our key management scheme include: 1. providing various parts of MANET the flexibility of selecting appropriate security configurations, according to the risks faced; 2. providing the adaptivity to cope with rapidly-changing environments; 3. handling of MANETs with a large number of nodes; 4. issuing certificates with different levels of assurance. We also propose two algorithms, which can be used independently from the hierarchical structure, to protect certification services in ad hoc networks from active attacks. Our simulation results show that, compared to the previous work [16,18,19], our second algorithm is much faster in a friendly environment. When the key length is 1024 bits, the process of generating or renewing a certificate in our second algorithm is around six to eight times faster, and the process of generating partial certificates in our second algorithm is around 20-80 times faster. The latter advantage is critical in MANET where intrinsically the less help a node requests from its neighbors, the higher is the chance of obtaining the help. Furthermore, simulation results also show that our two algorithms work well in a hostile environment in which existing schemes work poorly.
9542759
Defect-Tolerant Nanocomputing Using Bloom Filters
The authors propose a novel defect-tolerant design methodology using Bloom filters for defect mapping for nanoscale computing devices. It is a general approach that can be used for any permanent defects incurred during the manufacturing process. The redundant design methodology does not rely on a voting strategy, thus it utilizes the device redundancy more effectively than existing approaches. Additionally, our method does not have false-positive in defect identification, i.e. it will not report a defective device as functional. Moreover, it is very space economic and can be programmed to fit different scales and characteristics of the underlying specific nanoscale devices used in the system
12450638
A High Performance Application Representation for Reconfigurable Systems
Modern reconfigurable computing systems feature powerful hybrid architectures with multiple microprocessor cores, large reconfigurable logic arrays and distributed memory hierarchies. Mapping applications to these complex systems requires a representation that allows both hardware and software synthesis. Additionally, this representation must enable optimizations that exploit fine and coarse grained parallelism in order to effectively utilize the performance of the underlying reconfigurable architecture. Our work explores a representation based on the program dependence graph (PDG) incorporated with the static single-assignment (SSA) for synthesis to high performance reconfigurable devices. The PDG effectively describes control dependencies, while SSA yields precise data dependencies. When used together, these two representations provide a powerful, synthesizable form that exploits both fine and coarse grained parallelism. Compared to other commonly used representations for reconfigurable systems, the PDG+SSA form creates faster execution time, while using similar area.
47051192
Measurement-based analysis, modeling, and synthesis of the internet delay space