Zero-safe net models for transactions in Linda

Abstract Zero-safe nets are a variation of Petri nets, where transactions can be suitably modeled. The idea is to distinguish between stable places (whose markings define observable states) and zero-safe places (where tokens can only be temporarily allocated, defining hidden states): Transactions must start and end in observable states. We propose an extension of the coordination language Linda, called TraLinda, where a few basic primitives for expressing transactions are introduced by means of different typing of tuples. By exploiting previous results of Busi, Gorrieri and Zavattaro on the net modeling of Linda-like languages, we define a concurrent operational semantics based on zero-safe nets for TraLinda, where the typing of tuples reflects evidently on the distinction between stable and zero-safe places

A survey of the PEPA tools

This paper surveys the history and the current state of tool support for modelling with the PEPA stochastic process algebra and the PEPA nets modelling language. We discuss future directions for tool support for the PEPA family of languages.

Web Services and Models of Computation

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Financial Integration and International Risk Sharing

Conventional wisdom suggests that financial liberalization can help countries insure against idiosyncratic risk. There is little evidence, however, that countries have increased risk sharing despite recent widespread financial liberalization. This work shows that the key to understanding this puzzling observation is that conventional wisdom assumes frictionless international financial markets, while actual international financial markets are far from frictionless. In particular, financial contracts are incomplete and enforceability of debt repayment is limited. Default risk of debt contracts constrains borrowing, and more importantly, it makes borrowing more difficult in bad times, precisely when countries need insurance the most. Thus, default risk of debt contracts hinders international risk sharing. When countries remove their official capital controls, default risk is still present as an implicit barrier to capital flows; the observed increase in capital flows under financial liberalization is in fact too limited to improve risk sharing. If default risk of debt contracts were eliminated, capital flows would be six times greater, and international risk sharing would increase substantially.international risk sharing, financial integration, financial liberalization, financial frictions, sovereign default, international capital flows

Feedback Control Goes Wireless: Guaranteed Stability over Low-power Multi-hop Networks

Closing feedback loops fast and over long distances is key to emerging applications; for example, robot motion control and swarm coordination require update intervals of tens of milliseconds. Low-power wireless technology is preferred for its low cost, small form factor, and flexibility, especially if the devices support multi-hop communication. So far, however, feedback control over wireless multi-hop networks has only been shown for update intervals on the order of seconds. This paper presents a wireless embedded system that tames imperfections impairing control performance (e.g., jitter and message loss), and a control design that exploits the essential properties of this system to provably guarantee closed-loop stability for physical processes with linear time-invariant dynamics. Using experiments on a cyber-physical testbed with 20 wireless nodes and multiple cart-pole systems, we are the first to demonstrate and evaluate feedback control and coordination over wireless multi-hop networks for update intervals of 20 to 50 milliseconds.Comment: Accepted final version to appear in: 10th ACM/IEEE International Conference on Cyber-Physical Systems (with CPS-IoT Week 2019) (ICCPS '19), April 16--18, 2019, Montreal, QC, Canad

Costs and benefits of running an international currency

This report discusses the cost and benefits of running an international currency. It starts by discussing the effect of the euro's internationalization on financial markets, and presents data on the impact of the single currency on private credit. It considers recent work on the effect of the euro on financial integration and the implications of the euro's rising internationalization on the liquidity premium. Then it turns to the vehicle currency role of the euro and presents some results using new data from the latest BIS Triennial Survey on the foreign exchange market. Concerning the direct benefits of running an international currency, the report first offers estimates on the likely gains from international seigniorage and discuss work on the effects of the internationalization of the euro on the terms of trade and invoicing patterns in international trade. The implications of the international role of the euro for portfolio returns and the so-called “exorbitant privilege†are analysed in detail. The effects of the single currency on exchange rate volatility are also considered. It summarizes recent research on the impact of the euro on global bond and equity and analyzes the potential implications of the euro's international status for central banks' reserve holdings. Finally, it turns to the effects of the euro on the stability of domestic money demand and the problems posed for monetary policy, and the implications for international financial stability.euro, international currency, international role of the euro, Papaioannou , Portes , Costs and benefits of running an international currency

A Coordination Language for Databases

We present a coordination language for the modeling of distributed database applications. The language, baptized Klaim-DB, borrows the concepts of localities and nets of the coordination language Klaim but re-incarnates the tuple spaces of Klaim as databases. It provides high-level abstractions and primitives for the access and manipulation of structured data, with integrity and atomicity considerations. We present the formal semantics of Klaim-DB and develop a type system that avoids potential runtime errors such as certain evaluation errors and mismatches of data format in tables, which are monitored in the semantics. The use of the language is illustrated in a scenario where the sales from different branches of a chain of department stores are aggregated from their local databases. Raising the abstraction level and encapsulating integrity checks in the language primitives have benefited the modeling task considerably

Banking globalization, monetary transmission and the lending channel

The globalization of banking in the United States is influencing the monetary transmission mechanism both domestically and in foreign markets. Using quarterly information from all U.S. banks filing call reports between 1980 and 2005, we find evidence for the lending channel for monetary policy in large banks, but only those banks that are domestically-oriented and without international operations. We show that the large globally-oriented banks rely on internal capital markets with their foreign affiliates to help smooth domestic liquidity shocks. We also show that the existence of such internal capital markets contributes to an international propagation of domestic liquidity shocks to lending by affiliated banks abroad. While these results imply a substantially more active lending channel than documented in the seminal work of Kashyap and Stein (2000), the lending channel within the United States is declining in strength as banking becomes more globalized. --Lending channel,Bank,global,liquidity,transmission,internal capital markets