Lost in Abstraction: Monotonicity in Multi-Threaded Programs (Extended Technical Report)

Monotonicity in concurrent systems stipulates that, in any global state, extant system actions remain executable when new processes are added to the state. This concept is not only natural and common in multi-threaded software, but also useful: if every thread's memory is finite, monotonicity often guarantees the decidability of safety property verification even when the number of running threads is unknown. In this paper, we show that the act of obtaining finite-data thread abstractions for model checking can be at odds with monotonicity: Predicate-abstracting certain widely used monotone software results in non-monotone multi-threaded Boolean programs - the monotonicity is lost in the abstraction. As a result, well-established sound and complete safety checking algorithms become inapplicable; in fact, safety checking turns out to be undecidable for the obtained class of unbounded-thread Boolean programs. We demonstrate how the abstract programs can be modified into monotone ones, without affecting safety properties of the non-monotone abstraction. This significantly improves earlier approaches of enforcing monotonicity via overapproximations

CHINA'S RURAL HOUSEHOLD DEMAND FOR FRUIT AND VEGETABLES

A two-stage budgeting LES-LA/AIDS system is sued to estimate rural household demand in China with special emphasis on changes in demand for fruit and vegetable commodities across different income groups. The own-price elasticity for food was found to be more elastic than that for clothing, housing, durable goods, and other items. Within the food group, price elasticities range from -1.042 to -0.019. Grain, with an expenditure elasticity of almost unity, is an important staple food for the average rural household. Vegetables are important nonstaple foods relative to fruits. Lower value vegetables are the most price elastic in the vegetable group. Fruits are more price elastic than vegetables, with grapes being the most price elastic. Different income groups share a common demand function.AIDS model, Chinese rural households, Elasticity, Household demand, Household demand, LES model, Two-stage budgeting, Demand and Price Analysis,

Imports in the Washington State Economy: Importance and Regional Effects of Import Liberalization

This paper focuses on the import side of a regional economy quantifying the economic impact of import levels and trade liberalization. An innovation represents the linkage of a regional with a national model by combining two separate Computable General Equilibrium models into one framework. This allows for import price formation in liberalization scenarios on the national level and subsequent incorporation of these nationally simulated prices into the regional model. The regional model is applied to Washington State, one of the most trade dependent states of the U.S, the national model to the U.S. Data for the two identically structured models origin from the IMPLAN database which divides the U.S. and Washington economy into 509 industries. For both models, Monte Carlo techniques are used to mitigate parameter uncertainty inherent in CGE specifications. Two scenarios are simulated that differ in the assumptions about the macroeconomic and factor market adjustment options of the economies.Computable General equilibrium, regional modelling, trade liberalization, International Relations/Trade, C68, R13, F17,

RURAL-URBAN MIGRATION, LABOR MOBILITY AND AGRICULTURAL TRADE LIBERALIZATION IN CHINA

Under the terms of its accession to the WTO, China will likely commit to significant liberalization of its agricultural trade regimes. In this paper we consider how growing levels of urban unemployment, combined with a restrictive labor market policy, may alter the expected welfare effects of agricultural reform. We utilize a new AGE model of the Chinese economy based on the Harris-Todaro framework, incorporating imperfect labor mobility.International Relations/Trade, Labor and Human Capital,

CHINA'S ACCESSION TO THE WTO AND IMPACTS ON LIVESTOCK TRADE AND PRODUCTION PATTERNS

This paper was presented at the INTERNATIONAL TRADE IN LIVESTOCK PRODUCTS SYMPOSIUM in Auckland, New Zealand, January 18-19, 2001. The Symposium was sponsored by: the International Agricultural Trade Research Consortium, the Venture Trust, Massey University, New Zealand, and the Centre for Applied Economics and Policy Studies, Massey University. Dietary changes, especially in developing countries, are driving a massive increase in demand for livestock products. The objective of this symposium was to examine the consequences of this phenomenon, which some have even called a "revolution." How are dietary patterns changing, and can increased demands for livestock products be satisfied from domestic resources? If so, at what cost? What will be the flow-on impacts, for example, in terms of increased demands for feedgrains and the pressures for change within marketing systems? A supply-side response has been the continued development of large-scale, urban-based industrial livestock production systems that in many cases give rise to environmental concerns. If additional imports seem required, where will they originate and what about food security in the importing regions? How might market access conditions be re-negotiated to make increased imports achievable? Other important issues discussed involved food safety, animal health and welfare and the adoption of biotechnology, and their interactions with the negotiation of reforms to domestic and trade policies. Individual papers from this conference are available on AgEcon Search. If you would like to see the complete agenda and set of papers from this conference, please visit the IATRC Symposium web page at: http://www1.umn.edu/iatrc.intro.htmInternational Relations/Trade, Production Economics,

Bayesian Analysis of a Japanese Meat Demand System: A Robust Likelihood Approach

This paper presents an application of Bayesian analysis to an AIDS model of Japanese meat demand extending previous approaches in three ways: (1) The methodology employed is robust with respect to the likelihood function but retains the generic, easily programmable character of algorithms offered by Monte Carlo Integration approaches based on the normal likelihood function. (2) In addition to inequality constraints, linear exact restrictions and stochastic prior information are subjected to a Bayesian posterior analysis of validity and incorporated into Bayesian point estimates of model parameters and elasticities. (3) In order to assess the influence of the prior density on posterior distributions of model parameters relative to the likelihood, a measure quantifying the "degree of prior influence" on the posterior is defined. Das Diskussionspapier stellt eine Bayes'sche Analyse eines AIDS Modells Japanischer Fleischnachfrage vor, die eine Erweiterung fruherer Ansatze in den folgenden drei Punkten darstellt:(1) Die verwendete Methode ist robust bezuglich der Likelihood Funktion, erhalt dabei aber die Flexibilitat und einfache Umsetzung von Algorithmen basierend auf Monte Carlo Integration und der Annahme der Normalverteilung. (2) Zusatzlich zu Ungleichheitsbedingungen werden exakte Restriktionen und stochastische a-priori Information einer Bayes'schen a-posteriori Analyse unterzogen und in die Bayes'sche Punktschatzung von Parametern und Elastizitaten einbezogen. (3) Ein Index zur Messung des Einflusses der a-priori Information auf die a-posteriori Verteilung der Modellparameter wird vorgestellt.Demand and Price Analysis,