The goal of multi-winner elections is to choose a fixed-size committee based on voters’ preferences. An important concern in this setting is representation: large groups of voters with cohesive preferences should be adequately represented by the election winners. Recently, Aziz et al. proposed two axioms that aim to capture this idea: justified representation (JR) and its strengthening extended justified representation (EJR). In this paper, we extend the work of Aziz et al. in several directions. First, we answer an open question of Aziz et al., by showing that Reweighted Approval Voting satisfies JR for k = 3; 4; 5, but fails it for k >= 6. Second, we observe that EJR is incompatible with the Perfect Representation criterion, which is important for many applications of multi-winner voting, and propose a relaxation of EJR, which we call Proportional Justified Representation (PJR). PJR is more demanding than JR, but, unlike EJR, it is compatible with perfect representation, and a committee that provides PJR can be computed in polynomial time if the committee size divides the number of voters. Moreover, just like EJR, PJR can be used to characterize the classic PAV rule in the class of weighted PAV rules. On the other hand, we show that EJR provides stronger guarantees with respect to average voter satisfaction than PJR does.
Abstract. Web services are a very appropriate communication mechanism to perform distributed business processes among several organisations. These processes should be reliable, because a failure in them can cause high economic losses. To increase their reliability at design time, we have developed VERBUS, a framework for the formal verification of business processes. VERBUS can automatically translate business process definitions to specifications verifiable in several available tools. It is based on a modular and extensible architecture: new process definition languages and verification tools can be added easily to the framework. The prototype of VERBUS presented in this work can verify BPEL4WS process specifications, by translating them to Promela. The Promela specifications are verified with the well known model checker Spin. In this paper we describe the general architecture of VERBUS and how BPEL4WS specifications are translated and verified. The explanation is completed by describing what types of properties can be verified and providing an overview of the implementation.
In the current Information Society, being informed is a basic necessity. As one of the main news bussiness actors, news agencies are required to provide fresh, relevant, high-quality information to their customers. Dealing with this requirement is not an easy task, but, as partners of the NEWS (News Engine Web Services) project, we believe that the usage of Semantic Web technologies could help news agencies in achieving that objective. In this paper we will describe the aims and main achievements of the NEWS project, that was just completed. The NEWS Consortium is composed of news agencies Agencia EFE S.A.
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