IBM

About: IBM is a company organization based out in Armonk, New York, United States. It is known for research contribution in the topics: Layer (electronics) & Cache. The organization has 134567 authors who have published 253905 publications receiving 7458795 citations. The organization is also known as: International Business Machines Corporation & Big Blue.

Improved histograms for selectivity estimation of range predicates

Abstract: Many commercial database systems maintain histograms to summarize the contents of relations and permit efficient estimation of query result sizes and access plan costs. Although several types of histograms have been proposed in the past, there has never been a systematic study of all histogram aspects, the available choices for each aspect, and the impact of such choices on histogram effectiveness. In this paper, we provide a taxonomy of histograms that captures all previously proposed histogram types and indicates many new possibilities. We introduce novel choices for several of the taxonomy dimensions, and derive new histogram types by combining choices in effective ways. We also show how sampling techniques can be used to reduce the cost of histogram construction. Finally, we present results from an empirical study of the proposed histogram types used in selectivity estimation of range predicates and identify the histogram types that have the best overall performance.

A method and apparatus for screening audio-visual materials presented to a subscriber

Abstract: A method and apparatus for the automatic access control to multimedia presentations at the receiver in accordance with a viewer selected access mode and access classification data encoded into the multimedia presentation. Screening classification codes (SCCs) are embedded in the Audio Visual Material (AVM) delivered to a subscribers home station. The screening classification codes identify the type of content that follows in the AVM stream. For instance, violent content (video and/or audio) provided to a home station may contain a SCC that indicates violent scenes or violent action is forth coming in the AVM stream. The home station takes the SCC that are encoded and/or embedded in the AVM stream and applies a subscriber selected screening criteria. The screening criteria or suppression criteria are AVM manipulation commands. These AVM manipulation commands can blank the audio and/or video, cause the display of the last acceptable frame, perform obscuration transforms on the AVM stream or otherwise manipulate the audio and/or video portions of the AVM stream. The subscriber associates an AVM manipulation command with each of the available SCCs. The home station applies the subscriber desired manipulation commands to the AVM stream. Information on the subscriber selections are provided to an upstream node for subscriber behavior collection analysis.

A signature scheme with efficient protocols

Abstract: Digital signature schemes are a fundamental cryptographic primitive, of use both in its own right, and as a building block in cryptographic protocol design. In this paper, we propose a practical and provably secure signature scheme and show protocols (1) for issuing a signature on a committed value (so the signer has no information about the signed value), and (2) for proving knowledge of a signature on a committed value. This signature scheme and corresponding protocols are a building block for the design of anonymity-enhancing cryptographic systems, such as electronic cash, group signatures, and anonymous credential systems. The security of our signature scheme and protocols relies on the Strong RSA assumption. These results are a generalization of the anonymous credential system of Camenisch and Lysyanskaya.

Stark localization in GaAs-GaAlAs superlattices under an electric field.

Abstract: We have observed that a strong electric field $\mathcal{E}$ shifts to higher energies the photoluminescence and photocurrent peaks of a GaAs-${\mathrm{Ga}}_{0.65}$${\mathrm{Al}}_{0.35}$As superlattice of period $D$ (=65 \AA{}), which we explain by a field-induced localization of carriers to isolated quantum wells. Good agreement is found between observed and calculated shifts when the large field-induced increase of the exciton binding energy is taken into account. At moderate fields [\ensuremath{\cong}(2-3)\ifmmode\times\else\texttimes\fi{}${10}^{4}$ V/cm], the coupling between adjacent wells is manifested by four additional peaks that shift at the rates $\ifmmode\pm\else\textpm\fi{}e\mathcal{E}D$ and $\ifmmode\pm\else\textpm\fi{}2e\mathcal{E}D$ and correspond to transitions that involve different levels of the Stark ladder.