11,751 research outputs found
Compensation methods to support cooperative applications: A case study in automated verification of schema requirements for an advanced transaction model
Compensation plays an important role in advanced transaction models, cooperative work and workflow systems. A schema designer is typically required to supply for each transaction another transaction to semantically undo the effects of . Little attention has been paid to the verification of the desirable properties of such operations, however. This paper demonstrates the use of a higher-order logic theorem prover for verifying that compensating transactions return a database to its original state. It is shown how an OODB schema is translated to the language of the theorem prover so that proofs can be performed on the compensating transactions
Compensation methods to support generic graph editing: A case study in automated verification of schema requirements for an advanced transaction model
Compensation plays an important role in advanced transaction models, cooperative work, and workflow systems. However, compensation operations are often simply written as a^−1 in
transaction model literature. This notation ignores any operation parameters, results, and side effects. A schema designer intending to use an advanced transaction model is expected (required) to write correct method code. However, in the days of cut-and-paste, this is much easier said than done. In this paper, we demonstrate the feasibility of using an off-the-shelf theorem prover (also called a proof assistant) to perform automated verification of compensation requirements for an OODB schema. We report on the results of a case study in verification for a particular advanced transaction model that supports cooperative applications. The case study is based on an OODB schema that provides generic graph editing functionality for the creation, insertion, and manipulation of nodes and links
Coded Cooperative Data Exchange for a Secret Key
We consider a coded cooperative data exchange problem with the goal of
generating a secret key. Specifically, we investigate the number of public
transmissions required for a set of clients to agree on a secret key with
probability one, subject to the constraint that it remains private from an
eavesdropper.
Although the problems are closely related, we prove that secret key
generation with fewest number of linear transmissions is NP-hard, while it is
known that the analogous problem in traditional cooperative data exchange can
be solved in polynomial time. In doing this, we completely characterize the
best possible performance of linear coding schemes, and also prove that linear
codes can be strictly suboptimal. Finally, we extend the single-key results to
characterize the minimum number of public transmissions required to generate a
desired integer number of statistically independent secret keys.Comment: Full version of a paper that appeared at ISIT 2014. 19 pages, 2
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Detecting Byzantine Attacks Without Clean Reference
We consider an amplify-and-forward relay network composed of a source, two
relays, and a destination. In this network, the two relays are untrusted in the
sense that they may perform Byzantine attacks by forwarding altered symbols to
the destination. Note that every symbol received by the destination may be
altered, and hence no clean reference observation is available to the
destination. For this network, we identify a large family of Byzantine attacks
that can be detected in the physical layer. We further investigate how the
channel conditions impact the detection against this family of attacks. In
particular, we prove that all Byzantine attacks in this family can be detected
with asymptotically small miss detection and false alarm probabilities by using
a sufficiently large number of channel observations \emph{if and only if} the
network satisfies a non-manipulability condition. No pre-shared secret or
secret transmission is needed for the detection of these attacks, demonstrating
the value of this physical-layer security technique for counteracting Byzantine
attacks.Comment: 16 pages, 7 figures, accepted to appear on IEEE Transactions on
Information Forensics and Security, July 201
Facilitated spin models: recent and new results
Facilitated or kinetically constrained spin models (KCSM) are a class of
interacting particle systems reversible w.r.t. to a simple product measure.
Each dynamical variable (spin) is re-sampled from its equilibrium distribution
only if the surrounding configuration fulfills a simple local constraint which
\emph{does not involve} the chosen variable itself. Such simple models are
quite popular in the glass community since they display some of the peculiar
features of glassy dynamics, in particular they can undergo a dynamical arrest
reminiscent of the liquid/glass transitiom. Due to the fact that the jumps
rates of the Markov process can be zero, the whole analysis of the long time
behavior becomes quite delicate and, until recently, KCSM have escaped a
rigorous analysis with the notable exception of the East model. In these notes
we will mainly review several recent mathematical results which, besides being
applicable to a wide class of KCSM, have contributed to settle some debated
questions arising in numerical simulations made by physicists. We will also
provide some interesting new extensions. In particular we will show how to deal
with interacting models reversible w.r.t. to a high temperature Gibbs measure
and we will provide a detailed analysis of the so called one spin facilitated
model on a general connected graph.Comment: 30 pages, 3 figure
Strategyproof Profit Sharing in Partnerships: Improving upon Autarky
Several producers decide to form a partnership, to which they contribute both capital and labor. We propose a group-strategyproof mechanism under which no single agent is tempted to secede from the partnership: the inverse marginal product proportions (or IMPP) mechanism. The IMPP mechanism combines aspects of common ownership with the requirement that private property rights be respected: when an agent decides to stop exploiting her own capital, the latter is shared between the remaining agents in proportion to the productivity of their own capital. The IMPP is in fact the only fixed-path method (as introduced in Friedman, 2002) to satisfy autarkic individual rationality; its path is uniquely determined by the capital contributions of the agents. Thus, our results provide one of the first economic motivation for the asymmetry of fixed-path methods.
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