53,377 research outputs found
Finite-Blocklength Bounds for Wiretap Channels
This paper investigates the maximal secrecy rate over a wiretap channel
subject to reliability and secrecy constraints at a given blocklength. New
achievability and converse bounds are derived, which are shown to be tighter
than existing bounds. The bounds also lead to the tightest second-order coding
rate for discrete memoryless and Gaussian wiretap channels.Comment: extended version of a paper submitted to ISIT 201
Simulation Subsumption or DĂ©jĂ vu on the Web
Simulation unification is a special kind of unification adapted to retrieving semi-structured data on the Web. This article introduces simulation subsumption, or containment, that is, query subsumption under simulation unification. Simulation subsumption is crucial in general for query optimization, in particular for optimizing pattern-based search engines, and for the termination of recursive rule-based web languages such as the XML and RDF query language Xcerpt. This paper first motivates and formalizes simulation subsumption. Then, it establishes decidability of simulation subsumption for advanced query patterns featuring descendant constructs, regular expressions, negative subterms (or subterm exclusions), and multiple variable occurrences. Finally, we show that subsumption between two query terms can be decided in O(n!n) where n is the sum of the sizes of both query terms
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