Although the relational mode] for databases provides a great range of advantages over other data models, It lacks a comprehensive way to handle incomplete and uncertain data. Uncertainty in data values. however, is pervasive in all real-world environments and has i-eceiv[,d muc}] attent)[]n in the literature, Several methods ha}!e been proposed for incorporating uncertain data into relational databases.However, the current approaches have many shnrtcomlngs and havi, not established an acceptable extension af the relational model, In this paper. we propose :1 consistent extension of the relatiana] model. We present a revised relational structure and extend the relational algebra. The extended algebra ]s shown to be closed. N consistent extension of the conventiana] relational algebra, and reducible to tbe latt{,r ('at egorvcs and Subject

Outsourcing of software development allows a business to focus on its core competency and take advantage of vendors' technical expertise, economies of scale and scope, and their ability to smooth labor demand fluctuations across several clients. However, contracting a software project to an outside developer is often quite challenging because of information asymmetry and incentive divergence. A typical software development contract must deal with a variety of interrelated issues such as the quality of the developed system, the timeliness of delivery, the effort and cost associated with the project, the contract payment, and the postdelivery software support. This paper presents a contract-theoretic model that incorporates these factors to analyze how software outsourcing contracts can be designed. We find that despite their relative inefficiency, fixed-price contracts are often appropriate for simple software projects that require short development time. Time-and-materials contracts work well for more complex projects when the auditing process is efficient and effective. We also examine a type of performance-based contract called quality-level agreement and find that the first-best solution can be reached with such a contract. Finally, we consider profit-sharing contracts that are useful in situations where the developer has more bargaining power.

One of the most important concerns for managing public health is the prevention of infectious diseases. Although vaccines provide the most effective means for preventing infectious diseases, there are two main reasons why it is often difficult to reach a socially optimal level of vaccine coverage: (i) the emergence of operational issues (such as yield uncertainty) on the supply side, and (ii) the existence of negative network effects on the consumption side. In particular, uncertainties about production yield and vaccine imperfections often make manufacturing some vaccines a risky process and may lead the manufacturer to produce below the socially optimal level. At the same time, negative network effects provide incentives to potential consumers to free ride off the immunity of the vaccinated population. In this research, we consider how a central policy-maker can induce a socially optimal vaccine coverage through the use of incentives to both consumers and the vaccine manufacturer. We consider a monopoly market for an imperfect vaccine; we show that a fixed two-part subsidy is unable to coordinate the market, but derive a two-part menu of subsidies that leads to a socially efficient level of coverage.

It is commonly believed that piracy of information goods leads to lower profits, which translate to lower incentives to invest in innovation and eventually to lower-quality products. Manufacturers, policy makers, and researchers all claim that inadequate piracy enforcement efforts translate to lower investments in product development. However, we find many practical examples that contradict this claim. Therefore, to examine this claim more carefully, we develop a rigorous economic model of the manufacturer's quality decision problem in the presence of piracy. We consider a monopolist who does not have any marginal costs but has a product development cost quadratic in the quality level produced. The monopolist faces a consumer market heterogeneous in its preference for quality and offers a quality level that maximizes its profit. We also allow for the possibility that the manufacturer may use versioning to counter piracy. We unexpectedly find that in certain situations, lower piracy enforcement increases the monopolist's incentive to invest in quality. We explain the reasons and welfare implications of our findings. This paper was accepted by Lorin Hitt, information systems.

Prevention of infectious diseases is an important concern for managing public health. Although vaccines are the most effective means for preventing infectious diseases, the existence of a negative network externality often makes it difficult for vaccine coverage to reach a level that is socially optimal. In this research, we consider how a subsidy program can induce a socially optimal vaccine coverage. We consider an oligopoly market with identical vaccine producers and derive a subsidy that leads to a socially efficient level of coverage. We also derive a tax-subsidy combination that is revenue neutral, but achieves the same effect. Overall, our results provide useful insights for governments and policy makers with respect to an important issue related to public health.