Separating Without Any Ambiguity

We investigate a standard operator on classes of languages: unambiguous polynomial closure. We show that if C is a class of regular languages having some mild properties, the membership problem for its unambiguous polynomial closure UPol(C) reduces to the same problem for C. We give a new, self-contained and elementary proof of this result. We also show that unambiguous polynomial closure coincides with alternating left and right deterministic closure. Finally, if additionally C is finite, we show that the separation and covering problems are decidable for UPol(C)

Method and apparatus for measuring distance

The invention employs a continuous wave radar technique and apparatus which can be used as a distance measuring system in the presence of background clutter by utilizing small passive transponders. A first continuous electromagnetic wave signal S sub 1 at a first frequency f sub 1 is transmitted from a first location. A transponder carried by a target object positioned at a second (remote) location receives the transmitted signal, phase-coherently divides the f sub 1 frequency and its phase, and re-transmits the transmitted signal as a second continuous electromagnetic wave signal S sub 2 at a lower frequency f sub 2 which is a subharmonic of f sub 1. The re-transmitted signal is received at the first location where a measurement of the phase difference is made between the signals S sub 1 and S sub 2, such measuremnt being indicative of the distance between the first and second locations

Finite Automata for the Sub- and Superword Closure of CFLs: Descriptional and Computational Complexity

We answer two open questions by (Gruber, Holzer, Kutrib, 2009) on the state-complexity of representing sub- or superword closures of context-free grammars (CFGs): (1) We prove a (tight) upper bound of $2^{\mathcal{O}(n)}$ on the size of nondeterministic finite automata (NFAs) representing the subword closure of a CFG of size $n$. (2) We present a family of CFGs for which the minimal deterministic finite automata representing their subword closure matches the upper-bound of $2^{2^{\mathcal{O}(n)}}$ following from (1). Furthermore, we prove that the inequivalence problem for NFAs representing sub- or superword-closed languages is only NP-complete as opposed to PSPACE-complete for general NFAs. Finally, we extend our results into an approximation method to attack inequivalence problems for CFGs

Ambiguous Contracting: Natural Language and Judicial Interpretation

We study the relationship between ambiguity (which comes into the picture since contracts have to be written in natural language), and contractual incompleteness. The contracting process is modelled as a signalling game between the parties and the judge, with the contract as the signal. The judge is assumed to be bound by the content of the contract (in as far as it can be ascertained unambiguously). Two kind of examples are presented: The first set of examples shows how ambiguity can lead to incompleteness. Here incompleteness is a way of hedging against adverse judgements on the part of an imperfectly informed judge. The remaining example illustrates a sort of converse intuition: It shows how incompleteness might lead the contracting parties to write ambiguous contracts in order to afford a relatively well-informed judge freedom to enforce the parties'willincomplete contracts, natural language

Ambiguity of the Moment Tensor

An earthquake on a fault separating two dissimilar materials does not have a well-defined moment density tensor. We present a complete characterization of this bimaterial ambiguity in the general case of slip on a fault in an anisotropic medium. The ambiguity can be eliminated by utilizing a potency density rather than a moment density representation of a bimaterial source

Zero-error communication over networks

Zero-Error communication investigates communication without any error. By defining channels without probabilities, results from Elias can be used to completely characterize which channel can simulate which other channels. We introduce the ambiguity of a channel, which completely characterizes the possibility in principle of a channel to simulate any other channel. In the second part we will look at networks of players connected by channels, while some players may be corrupted. We will show how the ambiguity of a virtual channel connecting two arbitrary players can be calculated. This means that we can exactly specify what kind of zero-error communication is possible between two players in any network of players connected by channels.Comment: 10 pages, full version of the paper presented at the 2004 IEEE International Symposium on Information Theor