Aspects of Assembly and Cascaded Aspects of Assembly: Logical and Temporal Properties

Highly dynamic computing environments, like ubiquitous and pervasive computing environments, require frequent adaptation of applications. This has to be done in a timely fashion, and the adaptation process must be as fast as possible and mastered. Moreover the adaptation process has to ensure a consistent result when finished whereas adaptations to be implemented cannot be anticipated at design time. In this paper we present our mechanism for self-adaptation based on the aspect oriented programming paradigm called Aspect of Assembly (AAs). Using AAs: (1) the adaptations process is fast and its duration is mastered; (2) adaptations' entities are independent of each other thanks to the weaver logical merging mechanism; and (3) the high variability of the software infrastructure can be managed using a mono or multi-cycle weaving approach.Comment: 14 pages, published in International Journal of Computer Science, Volume 8, issue 4, Jul 2011, ISSN 1694-081

THE IMPORTANCE OF INCOME RISK IN LABOR ALLOCATION DECISIONS

Previous research has found that on-farm income variability helps determine off-farm labor supply. However, unobserved heterogeneity of farms or regions may have biased earlier results. In this study, we use an exogenous increase in Federal crop insurance subsidies as a natural experiment to identify the importance of risk in off-farm labor supply. The subsidy increases induced greater participation in crop insurance programs and thereby reduced farmers' financial risks. By merging county-level crop insurance participation data with farm-level Agricultural Census data from 1992 and 1997 we can compare the off-farm labor decisions of individual farms before and after the subsidy and thereby control for unobserved heterogeneity. Unlike previous studies, we find that on-farm risk does not affect the labor allocation decisions of farm households.Labor and Human Capital,

Evaluating a mobile telecommunications merger in Portugal

This paper evaluates the impact of the proposed Optimus-TMN mobile telecommunications merger in Portugal. The results suggest that, if the merger would have taken place, the average market profit margin would have increased by 11.6 percentage points and the average market price would have increased by 3.8%. As a consequence, the average marginal cost would have decreased by 14.9%, and welfare would have increased by €163.3mn per year, a gain entirely captured by the producers. Moreover, the merger would have resulted in a large transfer of surplus from consumers to producers, to the tune of €99.5mn per year. The conclusion is that, while the merger could have been authorized on efficiency grounds, such authorization should have been accompanied by strict retail price-cap merger remedies.info:eu-repo/semantics/publishedVersio

Merger Efficiency and Welfare Implications of Buyer Power

This paper analyzes the welfare implications of buyer mergers, which are mergers between downstream firms from different markets. We focus on the interaction between the merger's effects on downstream efficiency and on buyer power in a setup where one manufacturer with a non-linear cost function sells to two locally competitive retail markets. We show that size discounts for the merged entity has no impact on consumer prices or on smaller retailers, unless the merger affects the downstream efficiency of the merging parties. When the upstream cost function is convex, we find that there are "waterbed effects", that is, each small retailer pays a higher average tariff if a buyer merger improves downstream efficiency. We obtain the opposite results, "anti-waterbed effects", if the merger is inefficient. When the cost function is concave, there are only anti-waterbed effects. In each retail market, the merger decreases the final price if and only if it improves the efficiency of the merging parties, regardless of its impact on the average tariff of small retailers.Buyer mergers, non-linear supply contracts, merger efficiencies, size discounts, waterbed effects

Aspect-Oriented Programming

Aspect-oriented programming is a promising idea that can improve the quality of software by reduce the problem of code tangling and improving the separation of concerns. At ECOOP'97, the first AOP workshop brought together a number of researchers interested in aspect-orientation. At ECOOP'98, during the second AOP workshop the participants reported on progress in some research topics and raised more issues that were further discussed. \ud \ud This year, the ideas and concepts of AOP have been spread and adopted more widely, and, accordingly, the workshop received many submissions covering areas from design and application of aspects to design and implementation of aspect languages

Synthesis of Switching Protocols from Temporal Logic Specifications

We propose formal means for synthesizing switching protocols that determine the sequence in which the modes of a switched system are activated to satisfy certain high-level specifications in linear temporal logic. The synthesized protocols are robust against exogenous disturbances on the continuous dynamics. Two types of finite transition systems, namely under- and over-approximations, that abstract the behavior of the underlying continuous dynamics are defined. In particular, we show that the discrete synthesis problem for an under-approximation can be formulated as a model checking problem, whereas that for an over-approximation can be transformed into a two-player game. Both of these formulations are amenable to efficient, off-the-shelf software tools. By construction, existence of a discrete switching strategy for the discrete synthesis problem guarantees the existence of a continuous switching protocol for the continuous synthesis problem, which can be implemented at the continuous level to ensure the correctness of the nonlinear switched system. Moreover, the proposed framework can be straightforwardly extended to accommodate specifications that require reacting to possibly adversarial external events. Finally, these results are illustrated using three examples from different application domains

Information technology, capabilities and Asset Ownership: Evidence from Taxicab Fleets

We examine how information technology (IT) influences asset ownership through its impact on firms’ and agents’ capabilities. In particular, we propose that when IT is a substitute for agents’ industry-specific human capital, IT adoption leads to increased vertical integration. We test this prediction using micro data on vehicle ownership patterns from the Economic Census during a period when computerized dispatching systems were first adopted by taxicab firms. The empirical tests exploit exogenous variation in local market conditions, to identify the impact of dispatching technology on firm asset ownership. The results show that firms increase the proportion of taxicabs owned by 12% when they adopt new computerized dispatching systems. The findings suggest that firms increasingly vertically integrate when they acquire resources that substitute for their agents’ capabilities.

Does risk matter for farm businesses? The effect of crop insurance on production and diversification.

We use a large increase in Federal crop insurance subsidies as a natural experiment to identify the impact of risk on acreage and diversification decisions. Subsidy increases induced greater crop insurance coverage, which reduced farmers' financial risks. Did this change in the risk environment alter production decisions? We merged crop insurance participation data with farm-level Agricultural Census data from 1992 and 1997 to examine how harvested acreage and diversification changed in response to the policy-induced change in insurance coverage. The difference in differences empirical approach controls for unobservable heterogeneity and our results are robust across multiple definitions of our key variables and various fixed effects. We find that changes in the risk environment caused larger farms to expand while smaller farms shrank. Regardless of size, producers showed some evidence of using diversification as a method to mitigate risk. However, risk does not seem to have large overall effects.Risk and Uncertainty,

Acquisitions as a Response to Deregulation: Evidence from the Cable Television Industry

This paper studies the dynamics of an industry that is subject to exclusive geographical licensing. I develop a model of license ownership that predicts the evolution of profit-maximizing entry and acquisition decisions by firms over time, starting from an initial allocation of licenses. The entry and acquisition process is modeled as a one-sided coalition-formation game as in Farrell and Scotchmer (1988), where acquisition payoffs depend on economies of scale and agglomeration (economies of density). I estimate the model for the cable television industry in Canada using a panel that I have constructed from 1990 to 1996. The dataset builds up from the national regulator's license ownership decision files, and contains license-level information on acquisition decisions, subscribership, and subscription profits. The model is estimated in two steps. I first estimate firms' license-level profit functions, and then estimate the parameters of the fixed, merger and entry cost functions by Simulated Maximum Likelihood. Through counterfactual simulations, I use the estimated model to quantify the extent to which economies of scale and density drive acquisition behaviour, and to evaluate how merger activity reacts to a partial deregulation that occurs in 1994. Counterfactual experiments are also used to evaluate policies that stimulate entry or reduce acquisitions in the early years of the sample. The main finding is that these policies can lead to more productive dominant firms in the long-run as the industry consolidates.Acquisition, Entry, Coalition Formation, Economies of Density, Economies of Scale, Simulated Maximum Likelihood, Cable Television