In this paper, inspired in the field of belief revision, it is presented a novel operation for defining a new logic given a known logic. The operation consists in removing some (maybe undesirable) derived rule from a logic. Besides removing the ‘undesirable’ rule, this operation (called contraction) should change the logic in a minimal way. This paper presents formal definitions for contraction...

The public sector in developing countries is increasingly contracting with the non-state sector to improve access, efficiency and quality of health services. We conducted a multicountry study to assess the range of health services contracted out, the process of contracting and its influencing factors in ten countries of the Eastern Mediterranean Region: Afghanistan, Bahrain, Egypt, Islamic Repu...

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We analyze the contracting structure in a moral hazard setting with several agents where output is produced jointly and is the only contractible variable. Since the salary of each agent is a function of all agents efforts, a positive externality arises between them. This externality is not internalised by a centralised structure where the principal contracts directly with each agent. Instead, w...