3,718 research outputs found
A flexible mandatory access control policy for XML databases
A flexible mandatory access control policy (MAC) for XML
databases is presented in this paper. The label type and label
access policy can be defined according to the requirements of
applications. In order to preserve the integrity of data in XML
databases, a constraint between a read access rule and a write
access rule in label access policy is introduced. Rules for label
assignment and propagation are proposed to alleviate the
workload of label assignment. Also, a solution for resolving
conflicts of label assignments is proposed. At last, operations for
implementation of the MAC policy in a XML database are
illustrated
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A practical mandatory access control model for XML databases
A practical mandatory access control (MAC) model for XML databases is presented in this paper. The
label type and label access policy can be defined according to the requirements of different applications. In order to
preserve the integrity of data in XML databases, a constraint between a read-access rule and a write-access rule in
label access policy is introduced. Rules for label assignment and propagation are presented to alleviate the workload
of label assignments. Furthermore, a solution for resolving conflicts in label assignments is proposed. Rules for
update-related operations, rules for exceptional privileges of ordinary users and the administrator are also proposed
to preserve the security of operations in XML databases. The MAC model, we proposed in this study, has been
implemented in an XML database. Test results demonstrated that our approach provides rational and scalable
performance
Quantum entangled ground states of two spinor Bose-Einstein condensates
We revisit in detail the non-mean-field ground-state phase diagram for a
binary mixture of spin-1 Bose-Einstein condensates including quantum
fluctuations. The non-commuting terms in the spin-dependent Hamiltonian under
single spatial mode approximation make it difficult to obtain exact
eigenstates. Utilizing the spin z-component conservation and the total spin
angular momentum conservation, we numerically derive the information of the
building blocks and evaluate von Neumann entropy to quantify the ground states.
The mean-field phase boundaries are found to remain largely intact, yet the
ground states show fragmented and entangled behaviors within large parameter
spaces of interspecies spin-exchange and singlet-pairing interactions.Comment: 7 pages, 5 figure
A self-consistent Hartree-Fock approach for interacting bosons in optical lattices
A theoretical study of interacting bosons in a periodic optical lattice is
presented. Instead of the commonly used tight-binding approach (applicable near
the Mott insulating regime of the phase diagram), the present work starts from
the exact single-particle states of bosons in a cubic optical lattice,
satisfying the Mathieu equation, an approach that can be particularly useful at
large boson fillings. The effects of short-range interactions are incorporated
using a self-consistent Hartree-Fock approximation, and predictions for
experimental observables such as the superfluid transition temperature,
condensate fraction, and boson momentum distribution are presented.Comment: 12 pages, 15 figure file
A Non--Supersymmetric Dyonic Extreme Reissner--Nordstr\"{o}m Black Hole
We present a dyonic embedding of the extreme Reissner-Nordstr\"om black hole
in and supergravity that breaks all supersymmetries.Comment: A few references and comments have been adde
Cosmological solutions, p-branes and the Wheeler-DeWitt equation
The low energy effective actions which arise from string theory or M-theory
are considered in the cosmological context, where the graviton, dilaton and
antisymmetric tensor field strengths depend only on time. We show that previous
results can be extended to include cosmological solutions that are related to
the E_N Toda equations. The solutions of the Wheeler-DeWitt equation in
minisuperspace are obtained for some of the simpler cosmological models by
introducing intertwining operators that generate canonical transformations
which map the theories into free theories. We study the cosmological properties
of these solutions, and also briefly discuss generalised Brans-Dicke models in
our framework. The cosmological models are closely related to p-brane solitons,
which we discuss in the context of the E_N Toda equations. We give the explicit
solutions for extremal multi-charge (D-3)-branes in the truncated system
described by the D_4 =O(4,4) Toda equations.Comment: 11 pages (2-column), Revte
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