Nominal Logic Programming

Nominal logic is an extension of first-order logic which provides a simple foundation for formalizing and reasoning about abstract syntax modulo consistent renaming of bound names (that is, alpha-equivalence). This article investigates logic programming based on nominal logic. We describe some typical nominal logic programs, and develop the model-theoretic, proof-theoretic, and operational semantics of such programs. Besides being of interest for ensuring the correct behavior of implementations, these results provide a rigorous foundation for techniques for analysis and reasoning about nominal logic programs, as we illustrate via examples.Comment: 46 pages; 19 page appendix; 13 figures. Revised journal submission as of July 23, 200

Requirements for Provenance on the Web

From where did this tweet originate? Was this quote from the New York Times modified? Daily, we rely on data from the Web but often it is difficult or impossible to determine where it came from or how it was produced. This lack of provenance is particularly evident when people and systems deal with Web information or with any environment where information comes from sources of varying quality. Provenance is not captured pervasively in information systems. There are major technical, social, and economic impediments that stand in the way of using provenance effectively. This paper synthesizes requirements for provenance on the Web for a number of dimensions focusing on three key aspects of provenance: the content of provenance, the management of provenance records, and the uses of provenance information. To illustrate these requirements, we use three synthesized scenarios that encompass provenance problems faced by Web users toda

Finite and infinite support in nominal algebra and logic: nominal completeness theorems for free

By operations on models we show how to relate completeness with respect to permissive-nominal models to completeness with respect to nominal models with finite support. Models with finite support are a special case of permissive-nominal models, so the construction hinges on generating from an instance of the latter, some instance of the former in which sufficiently many inequalities are preserved between elements. We do this using an infinite generalisation of nominal atoms-abstraction. The results are of interest in their own right, but also, we factor the mathematics so as to maximise the chances that it could be used off-the-shelf for other nominal reasoning systems too. Models with infinite support can be easier to work with, so it is useful to have a semi-automatic theorem to transfer results from classes of infinitely-supported nominal models to the more restricted class of models with finite support. In conclusion, we consider different permissive-nominal syntaxes and nominal models and discuss how they relate to the results proved here

NASA Launch Services Program Small Satellite Processing Capabilities at Kennedy Space Center and Vandenberg Air Force Base

The NASA Launch Services Program (LSP) Launch Site Integration Branch (LSIB) conducted a study to identify options for accommodating launch site support requirements for the next generation of NASA small satellites and secondary payloads launched from the Kennedy Space Center (KSC) and Vandenberg Air Force Base (VAFB). The anticipated needs range from cleanroom facilities, to long-term secure hardware storage, to propellant loading/unloading, to stacking and fairing encapsulation. Existing commercial and government payload processing facilities (PPF) are highly capable and commonly used to support satellite processing, while alternate options may be better tailored for the needs and budgets of small satellites. These include peripheral facilities such as PPF airlocks or partitioned spaces, existing facilities which can be refurbished or upgraded, and portable facilities such as cleanroom trailers. The LSP LSIB continues to evaluate its capability to meet the needs of small satellites and secondary payloads. The author requests input from the small satellite community, to help identify any emerging launch site requirements for future NASA small satellite and secondary payload missions

Dynamic Excitation for Geotechnical Centrifuge Modelling

The method of physical modeling in the centrifuge is growing in acceptance in the U.S.A. following many years of use in U.S.S.R., Denmark, England, Norway, France and Japan. Simulation of dynamic events (machine vibration, wave forces, and earthquake) in modeling in the centrifuge has important applications, especially on the large national Geotechical Centrifuge being constructed at NASA-ARC. The most difficult problem is that of earthquake simulation. Several schemes for light weight shakers have been proposed in a Workshop on Dynamic Excitation for Geotechnical Centrifuge Model Testing held in August, 1979. More recently, a scheme has been presented which utilizes traveling waves generated through a diaphragm at the side of the container which has many promising advantages and does not negate the work done in shaker development, but improves their utilization

Causality and the semantics of provenance

Provenance, or information about the sources, derivation, custody or history of data, has been studied recently in a number of contexts, including databases, scientific workflows and the Semantic Web. Many provenance mechanisms have been developed, motivated by informal notions such as influence, dependence, explanation and causality. However, there has been little study of whether these mechanisms formally satisfy appropriate policies or even how to formalize relevant motivating concepts such as causality. We contend that mathematical models of these concepts are needed to justify and compare provenance techniques. In this paper we review a theory of causality based on structural models that has been developed in artificial intelligence, and describe work in progress on a causal semantics for provenance graphs.Comment: Workshop submissio

User's manual for the REEDM (Rocket Exhaust Effluent Diffusion Model) computer program

The REEDM computer program predicts concentrations, dosages, and depositions downwind from normal and abnormal launches of rocket vehicles at NASA's Kennedy Space Center. The atmospheric dispersion models, cloud-rise models, and other formulas used in the REEDM model are described mathematically Vehicle and source parameters, other pertinent physical properties of the rocket exhaust cloud, and meteorological layering techniques are presented as well as user's instructions for REEDM. Worked example problems are included