6,156 research outputs found

    Reliable scientific service compositions

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    Abstract. Distributed service oriented architectures (SOAs) are increas-ingly used by users, who are insufficiently skilled in the art of distributed system programming. A good example are computational scientists who build large-scale distributed systems using service-oriented Grid comput-ing infrastructures. Computational scientists use these infrastructure to build scientific applications, which are composed from basic Web ser-vices into larger orchestrations using workflow languages, such as the Business Process Execution Language. For these users reliability of the infrastructure is of significant importance and that has to be provided in the presence of hardware or operational failures. The primitives avail-able to achieve such reliability currently leave much to be desired by users who do not necessarily have a strong education in distributed sys-tem construction. We characterise scientific service compositions and the environment they operate in by introducing the notion of global scien-tific BPEL workflows. We outline the threats to the reliability of such workflows and discuss the limited support that available specifications and mechanisms provide to achieve reliability. Furthermore, we propose a line of research to address the identified issues by investigating auto-nomic mechanisms that assist computational scientists in building, exe-cuting and maintaining reliable workflows.

    Tensor products of maximal abelian subalgebras of C*-algebras

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    It is shown that if C1C_1 and C2C_2 are maximal abelian self-adjoint subalgebras (masas) of C*-algebras A1A_1 and A2A_2, respectively, then the completion C1C2C_1\otimes C_2 of the algebraic tensor product C1C2C_1\odot C_2 of C1C_1 and C2C_2 in any C*-tensor product A1βA2A_1\otimes_{\beta} A_2 is maximal abelian provided that C1C_1 has the extension property of Kadison and Singer and C2C_2 contains an approximate identity for A2A_2. An example is given to show that C1C2C_1\otimes C_2 can fail to be a masa in A1βA2A_1\otimes_{\beta} A_2 with A1A_1 and A2A_2 unital if neither C1C_1 nor C2C_2 has the extension property. This gives an answer to a long-standing question, but leaves open some other interesting problems, one of which turns out to have a potentially intriguing implication for the Kadison-Singer extension problem.Comment: 10 pages. Revision 1. Simplifications in the examples in section 3, original first paragraph of section 4 delete

    The order of the automorphism group of a binary qq-analog of the Fano plane is at most two

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    It is shown that the automorphism group of a binary qq-analog of the Fano plane is either trivial or of order 22.Comment: 10 page