34190440
Coercive subtyping for the calculus of constructions
1048322
Soundness of Coercion in the Calculus of Constructions
A coercive subtyping system for the Calculus of Constructions is presented. The proposed system λC≤co is obtained essentially by adding coercions and η-conversion to λC≤, which is a subtyping extension to the Calculus of Constructions without coercions. We proved that a coercion c:A ≤ B is semantically sound. That is, (1) c is a term of type A → B; (2) c behaves like an identity function. This development follows the spirit of semantical interpretation of subtyping.
6370123
Full integration of subtyping and if-expression
The combination of full subsumption and conditional expression is a challenging problem, because in such a system, a term might not have a type which is a representative of all types of the term. Therefore, the traditional type checking technique fails. Due to such a difficulty, Java typing rule for if-expression uses only a restricted form of subtyping. In this paper, we propose a type system which includes both of the above mentioned features and enjoys decidable type checking. We also show that the system has the subject reduction property. It is expected that this technique could be used to improve the type system of Java with full subsumption.
33357953
PISA: Federated Search in P2P Networks with Uncooperative Peers
Recently, federated search in P2P networks has received much attention. Most of the previous work assumed a cooperative environment where each peer can actively participate in information publishing and distributed document indexing. However, little work has addressed the problem of incorporating uncooperative peers, which do not publish their own corpus statistics, into a network. This paper presents a P2P-based federated search framework called PISA which incorporates uncooperative peers as well as the normal ones. In order to address the indexing needs for uncooperative peers, we propose a novel heuristic query-based sampling approach which can obtain high-quality resource descriptions from uncooperative peers at relatively low communication cost. We also propose an effective method called RISE to merge the results returned by uncooperative peers. Our experimental results indicate that PISA can provide quality search results, while utilizing the uncooperative peers at a low cost.
16964451
HISA: a query system bridging the semantic gap for large image databases
We propose a novel system called HISA for organizing very large image databases. HISA implements the first known data structure to capture both the ontological knowledge and visual features for effective and effcient retrieval of images by either keywords, image examples, or both. HISA employs automatic image annotation technique, ontology analysis and statistical analysis of domain knowledge to precompute the data structure. Using these techniques, HISA is able to bridge the gap between the image semantics and the visual features, therefore providing more user-friendly and high-performance queries. We demonstrate the novel data structure employed by HISA, the query algorithms, and the pre-computation process.
2171580
Dependent Types with Subtyping and Late-Bound Overloading
We present a calculus with dependent types, subtyping, and late-bound overloading. Besides its theoretical interest this work is motivated by several practical needs that range form the definition of logic encodings to proof specialization and reuse and to object-oriented extension of the SML module system. The theoretical study of this calculus is not straightforward. While confluence is relatively easy to prove, subject reduction is much harder. We were not able to add overloading to any existing system with dependent types and subtyping, and prove subject reduction. This is why we also define here as by-product a new subtyping system for dependent types that improves previous systems and enjoys several properties (notably the transitivity elimination property). The calculus with overloading is then obtained as a conservative extension of this new system. Another difficult point is strong normalization, which is a necessary condition to the decidability of subtyping and typing relations. The calculus with overloading is not strongly normalizing. However, we show that a reasonably useful fragment of the calculus enjoys this property and that its strong normalization implies the decidability of its subtyping and typing relations. The article is divided into two parts: the first three scetions provide a general overview of the systems and its motivations and can be read separately; the remaining sections develop the formal study.
6110208
Nanophotonics — Quantum dots, photonic crystals, and optical silicon circuits: An excursion into the optical behavior of very small things
This paper covers four specific areas — diverse in their scope and approach — of nanophotonics research at Bell Labs, ranging from nanosized light emitters to passive and active optical circuits fabricated or actuated with nanometer precision. Our first example involves the dynamics of carriers confined in quantum dots fabricated via self-assembly on semiconducting substrates; we show that the evolution of carrier populations is a result of the interplay of interactions between photons, phonons, electrons, and holes. A second example involves a nanosize light-emitting quantum dot system that is fabricated by embedding passivated spherical semiconducting quantum dots in a polymer matrix; the fabrication steps and subsequent optical measurements, including the observation of net optical gain in this system, are described. In the area of passive and active optical circuits, we report on efforts to optimize the transmission efficiencies of photonic crystal circuit-building elements (e.g., waveguide bends and waveguide tapers in passive two-dimensional photonic crystal circuits). Finally, we describe active optical silicon circuits fabricated on a silicon-on-insulator platform; these devices comprise waveguide interferometers and electrostatically actuated piston micromirrors, and they require nanometer-size displacements to function as optical switches with inherently low power consumption.
22227630
An Index Scheme for XML Documents Based on Relationship Joins
XML is rapidly emerging as a standard for information storage, representation and exchange on the Web. How to rapidly search and query XML documents efficiently has received many attentions in resent research. However, current querying schemes of XML documents typically involve in both node content and tree structural information, which may limit efficiency when facing the application that the tree structural information is more complicated than the tree node itself. In this paper, we propose the node relationships joins algorithms that utilize available indexes mainly on tree structural information. The relationships join algorithms work perfectly especially for searching paths that are very long or whose lengths are unknown. Experimental results from our prototype system implementation highlight the correctness and efficiency of our solution