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Institution

AT&T Labs

Company
About: AT&T Labs is a based out in . It is known for research contribution in the topics: Network packet & The Internet. The organization has 1879 authors who have published 5595 publications receiving 483151 citations.


Papers
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Proceedings ArticleDOI
Pete Epstein1, Ravi Sandhu
28 Oct 1999
TL;DR: This paper represents an existing Role framework recently published by Thomsen, O’Brien, and Bogle, and concludes that this framework can be modeled in UML, with the assistance of adding a new user defined UML vocabulary.
Abstract: Role based access control (RBAC) is a promising technology for scalable access control. For RBAC to rise to its full potential, the roles must be properly constructed to reflect organizational access control policy and needs. This requires a discipline of Role Engineering to develop various components of RBAC such as role hierarchy, permissions (and permissionrole assignment), and constraints. The importance of Role Engineering has been recognized but very little work has been done to date. In this paper we explore the possibility of using the Unified Modeling Language (UML) to support Role Engineering. We chose UML because it is a de facto standard and refIects a consensus in the modeling community. To investigate the capability of UML for Role Engineering, we represent an existing Role framework recently published by Thomsen, O’Brien, and Bogle. This framework can be modeled in UML, with the assistance of adding a new user defined UML vocabulary.

94 citations

Journal ArticleDOI
TL;DR: In this paper, the authors investigate using Fabry-Perot lasers as the upstream transmitters in a WDM-PON, and demonstrate transmission of a 10-Mb/s signal through each port of a wavelength-grating router followed by 18 km of fiber using an uncooled FabryPerot laser.
Abstract: We investigate using Fabry-Perot lasers as the upstream transmitters in a wavelength-division-multiplexed passive optical network (WDM-PON). We demonstrate transmission of a 10-Mb/s signal through each port of a wavelength-grating router followed by 18 km of fiber using an uncooled Fabry-Perot laser. These signals could be subcarrier multiplexed together, so that each user would have a dedicated radio-frequency channel. Since Fabry-Perot lasers provide more output power than low-cost light-emitting diodes, this may enable deployment of WDM-PON's in areas where optical loss prohibits the use of other low cost optical sources. The bit-rate is limited by mode-fluctuations being converted into intensity noise when transmitted through the router.

94 citations

Book ChapterDOI
26 Oct 2000
TL;DR: This work examines several different medium-size poker variants and gives encouraging results for abstraction-based methods on these games, specifically variants of poker.
Abstract: ion is a method often applied to keep the combinatorial explosion under control and to solve problems of large complexity. Ourwork focuses on applying abstraction to solve large stochastic imperfect-information games, specifically variants of poker.We examine several different medium-size poker variants and give encouraging results for abstraction-based methods on these games.

94 citations

Journal ArticleDOI
TL;DR: The authors discuss the proposition that most of the temporal PMD changes that are observed in installed routes arise primarily from a relatively small number of "hot spots" along the route that are exposed to the ambient environment, whereas the buried shielded sections remain largely stable for month-long time periods.
Abstract: Polarization mode dispersion (PMD), a potentially limiting impairment in high-speed long-distance fiber-optic communication systems, refers to the distortion of propagating optical pulses due to random birefringences in an optical system. Because these perturbations (which can be introduced through manufacturing imperfections, cabling stresses, installation procedures, and environmental sensitivities of fiber and other in-line components) are unknowable and continually changing, PMD is unique among optical impairments. This makes PMD both a fascinating research subject and potentially one of the most challenging technical obstacles for future optoelectronic transmission. Mitigation and compensation techniques, proper emulation, and accurate prediction of PMD-induced outage probabilities critically depend on the understanding and modeling of the statistics of PMD in installed links. Using extensive data on buried fibers used in long-haul high-speed links, the authors discuss the proposition that most of the temporal PMD changes that are observed in installed routes arise primarily from a relatively small number of "hot spots" along the route that are exposed to the ambient environment, whereas the buried shielded sections remain largely stable for month-long time periods. It follows that the temporal variations of the differential group delay for any given channel constitute a distinct statistical distribution with its own channel-specific mean value. The impact of these observations on outage statistics is analyzed, and the implications for future optoelectronic fiber-based transmission are discussed

94 citations

Journal ArticleDOI
01 Aug 2009
TL;DR: This paper proposes a principled approach to summarizing the contents of a relational database, so that a user can determine at a glance the type of information it contains, and the main tables in which that information resides, and shows that it achieves significantly higher accuracy than the previous state of the art, but is also faster and scales linearly with the size of the schema graph.
Abstract: Complex databases are challenging to explore and query by users unfamiliar with their schemas. Enterprise databases often have hundreds of inter-linked tables, so even when extensive documentation is available, new users must spend a considerable amount of time understanding the schema before they can retrieve any information from the database. The problem is aggravated if the documentation is missing or outdated, which may happen with legacy databases.In this paper we identify limitations of previous approaches to address this vexing problem, and propose a principled approach to summarizing the contents of a relational database, so that a user can determine at a glance the type of information it contains, and the main tables in which that information resides. Our approach has three components: First, we define the importance of each table in the database as its stable state value in a random walk over the schema graph, where the transition probabilities depend on the entropies of table attributes. This ensures that the importance of a table depends both on its information content, and on how that content relates to the content of other tables in the database. Second, we define a metric space over the tables in a database, such that the distance function is consistent with an intuitive notion of table similarity. Finally, we use a Weighted k-Center algorithm under this distance function to cluster all tables in the database around the most relevant tables, and return the result as our summary. We conduct an extensive experimental study on a benchmark database, comparing our approach with previous methods, as well as with several hybrid models. We show that our approach not only achieves significantly higher accuracy than the previous state of the art, but is also faster and scales linearly with the size of the schema graph.

93 citations


Authors

Showing all 1881 results

NameH-indexPapersCitations
Yoshua Bengio2021033420313
Scott Shenker150454118017
Paul Shala Henry13731835971
Peter Stone130122979713
Yann LeCun121369171211
Louis E. Brus11334763052
Jennifer Rexford10239445277
Andreas F. Molisch9677747530
Vern Paxson9326748382
Lorrie Faith Cranor9232628728
Ward Whitt8942429938
Lawrence R. Rabiner8837870445
Thomas E. Graedel8634827860
William W. Cohen8538431495
Michael K. Reiter8438030267
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Performance
Metrics
No. of papers from the Institution in previous years
YearPapers
20225
202133
202069
201971
2018100
201791