Size-Change Termination as a Contract

Termination is an important but undecidable program property, which has led to a large body of work on static methods for conservatively predicting or enforcing termination. One such method is the size-change termination approach of Lee, Jones, and Ben-Amram, which operates in two phases: (1) abstract programs into "size-change graphs," and (2) check these graphs for the size-change property: the existence of paths that lead to infinite decreasing sequences. We transpose these two phases with an operational semantics that accounts for the run-time enforcement of the size-change property, postponing (or entirely avoiding) program abstraction. This choice has two key consequences: (1) size-change termination can be checked at run-time and (2) termination can be rephrased as a safety property analyzed using existing methods for systematic abstraction. We formulate run-time size-change checks as contracts in the style of Findler and Felleisen. The result compliments existing contracts that enforce partial correctness specifications to obtain contracts for total correctness. Our approach combines the robustness of the size-change principle for termination with the precise information available at run-time. It has tunable overhead and can check for nontermination without the conservativeness necessary in static checking. To obtain a sound and computable termination analysis, we apply existing abstract interpretation techniques directly to the operational semantics, avoiding the need for custom abstractions for termination. The resulting analyzer is competitive with with existing, purpose-built analyzers

UK domestic energy contracts, the 28 day rule, and experience in Sweden

In the UK, domestic customers must be able to terminate energy contracts at 28 days� notice. This has been seen as a transitional protection for customers and for competition. This paper reviews the arguments for and against the 28 day rule, and examines the extent to which UK suppliers have offered fixed-price fixed-term contracts. It also looks at experience in Sweden, where there is no such restriction and where there is greater use of fixed-price fixed-term contracts. The paper concludes that there is no longer a need for the 28 day rule to protect customers, and that it is more likely to restrict than to protect competition

Problems Affecting Labor

Much experimental work has been devoted in comparing the folding behavior of proteins sharing the same fold but different sequence. The recent design of proteins displaying very high sequence identities but different 3D structure allows the unique opportunity to address the protein-folding problem from a complementary perspective. Here we explored by ℙ-value analysis the pathways of folding of three different heteromorphic pairs, displaying increasingly high-sequence identity (namely, 30%, 77%, and 88%), but different structures called G A (a 3-α helix fold) and G B (an α/β fold). The analysis, based on 132 site-directed mutants, is fully consistent with the idea that protein topology is committed very early along the pathway of folding. Furthermore, data reveals that when folding approaches a perfect two-state scenario, as in the case of the G A domains, the structural features of the transition state appear very robust to changes in sequence composition. On the other hand, when folding is more complex and multistate, as for the G Bs, there are alternative nuclei or accessible pathways that can be alternatively stabilized by altering the primary structure. The implications of our results in the light of previous work on the folding of different members belonging to the same protein family are discussed

The Incidence and Cost of Job Loss in a Transition Economy: Displaced Workers in Estonia, 1989-1999

We examine the pattern and costs of worker displacement in one of the more reform- oriented transition countries, Estonia, as the transition process develops. Using Labour Force Survey data covering the period 1989-1999, we show that after the initial shock, displacement rates in Estonia have fallen back to levels observed in several western economies, as the economy picks up. The incidence of displacement is also similar to that in the West – concentrated on the less skilled and those with short job tenure. Roughly half of those displaced find re-employment within two months while the other half lingers on in the state of non-employment. There is less evidence however of a wage penalty to job loss, unlike in some Western countries, a fact one might attribute more to the nature of the transition process than to wage setting institutions in Estonia. The main cost of displacement is then the income loss due to non-employment, which is severe for a minority of workers who experience long-term non-employment.http://deepblue.lib.umich.edu/bitstream/2027.42/39874/3/wp489.pd

Pay-performance Sensitivity and Firm Size: Insights From the Mutual Fund Industry

I examine the ex ante decision to make an agent\u27s pay-performance sensitivity an inverse function of organization size. I focus on mutual funds and their decision to use compensation contracts that reduce the advisor\u27s marginal compensation as the fund grows (a declining-rate contract) over the dominant contract type, where marginal compensation is unrelated to fund size (a single-rate contract). I find evidence consistent with the view that declining-rate contracts are a mechanism to keep marginal compensation in line with the advisor\u27s declining marginal product. Specifically, I find that funds with greater exposure to diseconomies of scale are more likely to use a declining-rate contract and to specify a greater amount of compensation decline in their contracts. Consistent with optimal contracting, I find no evidence of a performance difference between funds with declining-rate contracts and funds with single-rate contracts

Breaking New Ground in Germany: Work Visa and Labour Law Aspects

[Excerpt] The purpose of this booklet is to provide a summary of the laws and procedures applicable to anyone who enters Germany and takes up employment. It does not explore all issues in detail.The law is correct as of April 1, 2006

The effects of contract detail and prior ties on contract change : a learning perspective

Despite the large literature on alliance contract design, we know little about how transacting parties change and amend their underlying contracts during the execution of strategic alliances. Drawing on existing research in the alliance contracting literature, we develop the empirical question of how contract detail and prior ties influence the amount, direction, and type of change in such agreements during the collaboration. We generated a sample of 115 joint ventures (JVs) by distributing a survey to JV board members or top managers and found that the amount of contract change is negatively associated with the level of detail in the initial contract but is positively associated with the number of prior ties between alliance partners. In relation to the direction of contract change, we find that the level of detail of the initial agreements negatively correlates with the likelihood of removing or weakening existing provisions and that prior collaborative experience positively correlates with the likelihood of strengthening of existing provisions or adding of new ones. We also find that prior ties affect the type of change in that JV parents prefer to change enforcement provisions more so than the coordination provisions in the contract. Our paper generates new insights on the complementarities between relational governance and transaction cost economics perspectives on alliance contracting