Uniform Substitution for Differential Game Logic

This paper presents a uniform substitution calculus for differential game logic (dGL). Church's uniform substitutions substitute a term or formula for a function or predicate symbol everywhere. After generalizing them to differential game logic and allowing for the substitution of hybrid games for game symbols, uniform substitutions make it possible to only use axioms instead of axiom schemata, thereby substantially simplifying implementations. Instead of subtle schema variables and soundness-critical side conditions on the occurrence patterns of logical variables to restrict infinitely many axiom schema instances to sound ones, the resulting axiomatization adopts only a finite number of ordinary dGL formulas as axioms, which uniform substitutions instantiate soundly. This paper proves soundness and completeness of uniform substitutions for the monotone modal logic dGL. The resulting axiomatization admits a straightforward modular implementation of dGL in theorem provers

A Complete Axiomatization of Quantified Differential Dynamic Logic for Distributed Hybrid Systems

We address a fundamental mismatch between the combinations of dynamics that occur in cyber-physical systems and the limited kinds of dynamics supported in analysis. Modern applications combine communication, computation, and control. They may even form dynamic distributed networks, where neither structure nor dimension stay the same while the system follows hybrid dynamics, i.e., mixed discrete and continuous dynamics. We provide the logical foundations for closing this analytic gap. We develop a formal model for distributed hybrid systems. It combines quantified differential equations with quantified assignments and dynamic dimensionality-changes. We introduce a dynamic logic for verifying distributed hybrid systems and present a proof calculus for this logic. This is the first formal verification approach for distributed hybrid systems. We prove that our calculus is a sound and complete axiomatization of the behavior of distributed hybrid systems relative to quantified differential equations. In our calculus we have proven collision freedom in distributed car control even when an unbounded number of new cars may appear dynamically on the road

A Uniform Substitution Calculus for Differential Dynamic Logic

This paper introduces a new proof calculus for differential dynamic logic (dL) that is entirely based on uniform substitution, a proof rule that substitutes a formula for a predicate symbol everywhere. Uniform substitutions make it possible to rely on axioms rather than axiom schemata, substantially simplifying implementations. Instead of nontrivial schema variables and soundness-critical side conditions on the occurrence patterns of variables, the resulting calculus adopts only a finite number of ordinary dL formulas as axioms. The static semantics of differential dynamic logic is captured exclusively in uniform substitutions and bound variable renamings as opposed to being spread in delicate ways across the prover implementation. In addition to sound uniform substitutions, this paper introduces differential forms for differential dynamic logic that make it possible to internalize differential invariants, differential substitutions, and derivations as first-class axioms in dL

U.S. Travel and Tourism: Industry Trends and Policy Issues for Congress

[Excerpt] The travel and tourism industry is an amalgam of business activities including transportation, lodging, entertainment, meals, and retail trade. Collectively, this mature sector of the U.S. economy accounts for 2.8% of U.S. gross domestic product (GDP) and directly employs 5.7 million Americans. While they have increased in recent years, employment and real output in travel and tourism have not fully recovered from the 2007-2009 recession. It is in this context that Congress will consider whether to reauthorize or extend the Travel Promotion Act of 2009 (TPA; P.L. 111-145), which established a national advertising and marketing effort to encourage international visitors to spend time in the United States. The law is scheduled to expire at the end of FY2015. A number of other bills intended to make travel to the United States less complicated for foreign visitors also await action in Congress. action in Congress

Pending U.S. and EU Free Trade Agreements with South Korea: Possible Implications for Automobile and Other Manufacturing Industries

[Excerpt] South Korea has negotiated free trade agreements (FTAs) with the United States and the European Union (EU), but neither agreement has yet been approved. The U.S. Congress must approve the United States and South Korea free trade agreement (KORUS FTA) and the European Parliament must vote on the European Union and South Korea free trade agreement (KOREU FTA) before the FTAs can take effect. If the FTAs are ratified, it is possible there could be a “first mover” advantage for either the United States or the European Union, depending on which FTA is approved first. Some argue that both agreements have shortcomings and should not be approved. This report provides U.S. lawmakers with a comparison of the manufacturing components in the KORUS and KOREU FTAs. Congressional interest in an FTA between the European Union and South Korea mostly centers on those U.S. industries competing with European industrial sectors, especially motor vehicles. The two pending FTAs raise questions about what it could mean for U.S. manufacturers if the United States takes longer, or fails altogether, to implement the KORUS FTA, while the European Union and South Korea possibly move ahead to approve and implement their outstanding FTA. In such a case, the possibility exists that the removal of tariff and nontariff barriers between the European Union and South Korean markets could result in U.S. manufacturers losing South Korean market share to European competitors. On balance, most U.S. and European manufacturing sectors, with some auto manufacturers in particular among notable dissenters, argue that the pending FTAs will be beneficial and are largely supportive. On the other side, labor unions in the United States and the European Union are considerably more skeptical, claiming that South Korean companies could be the biggest beneficiaries, since they could gain even greater access to the significantly larger U.S. and EU markets. Labor union leaders say the FTA will result in further job losses as their respective manufacturing workforces compete for market share with competitive South Korean manufacturers in their own domestic markets

On the need for a global engineering initiative to mitigate climate change

There is growing scientific evidence that the continued emission of greenhouse gases will eventually lead to catastrophic irreversible climate change and that, therefore, a global effort needs to be started to transition to a fully renewable economy. In this article, the engineering challenges of converting to emission-free power generation are reviewed and the feasibility of two proposed solutions, i.e. the ‘wind–water–solar’ and the ‘energy ship’ proposals, are discussed. It is concluded that a well-conceived and executed engineering effort needs to be initiated and guided by a Global Engineering Council for the purpose of examining and ranking various proposals and making specific recommendations