The Method of Equal Shares (ES) is a popular approval-based multi-winner voting rule, which was originally proposed by Peters and Skowron. It satisfies several well-known representation axioms, like extended justified representation (EJR) and priceability, and it can be computed in polynomial time. Further, it has already been employed in several real participatory budgeting elections. In this note, we prove that ES is an instance of the EJR-Exact family of voting rules that also satisfy EJR and were proposed by Aziz et al. 2018 before the work of Peters and Skowron. • EJR-Exact is a broad family of approval-based multi-winner voting rules. • All the voting rules in the EJR-Exact family satisfy EJR and EJR+. • Many rules in the EJR-Exact family can be computed in polynomial time. • We prove that the popular Method of Equal Shares is a particular instance of this family.

We provide the first large-scale data collection of real-world approval-based committee elections. These elections have been conducted on the Polkadot blockchain as part of their Nominated Proof-of-Stake mechanism and contain around one thousand candidates and tens of thousands of (weighted) voters each. We conduct an in-depth study of application-relevant questions, including a quantitative and qualitative analysis of the outcomes returned by different voting rules. Besides considering proportionality measures that are standard in the multiwinner voting literature, we pay particular attention to less-studied measures of overrepresentation, as these are closely related to the security of the Polkadot network. We also analyze how different design decisions such as the committee size affect the examined measures.

We propose the maximin support method, a novel extension of the D'Hondt apportionment method to approval-based multiwinner elections. The maximin support method is a sequential procedure that aims to maximize the support of the least supported elected candidate. It can be computed efficiently and satisfies (adjusted versions of) the main properties of the original D'Hondt method: house monotonicity, population monotonicity, and proportional representation. We also establish a close relationship between the maximin support method and alternative D'Hondt extensions due to Phragmén.

We consider the problem of selecting a fixed-size committee based on approval ballots. It is desirable to have a committee in which all voters are fairly represented. Aziz et al. (2015a; 2017) proposed an axiom called extended justified representation (EJR), which aims to capture this intuition; subsequently, Sanchez-Fernandez et al. (2017) proposed a weaker variant of this axiom called proportional justified representation (PJR). It was shown that it is coNP-complete to check whether a given committee provides EJR, and it was conjectured that it is hard to find a committee that provides EJR. In contrast, there are polynomial-time computable voting rules that output committees providing PJR, but the complexity of checking whether a given committee provides PJR was an open problem. In this paper, we answer open questions from prior work by showing that EJR and PJR have the same worst-case complexity: we provide two polynomial-time algorithms that output committees providing EJR, yet we show that it is coNP-complete to decide whether a given committee provides PJR. We complement the latter result by fixed-parameter tractability results.

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.

In recent years, big data systems have become an active area of research and development. Stream processing is one of the potential application scenarios of big data systems where the goal is to process a continuous, high velocity flow of information items. High frequency trading (HFT) in stock markets or trending topic detection in Twitter are some examples of stream processing applications. In some cases (like, for instance, in HFT), these applications have end-to-end quality-of-service requirements and may benefit from the usage of real-time techniques. Taking this into account, the present article analyzes, from the point of view of real-time systems, a set of patterns that can be used when implementing a stream processing application. For each pattern, we discuss its advantages and disadvantages, as well as its impact in application performance, measured as response time, maximum input frequency and changes in utilization demands due to the pattern.

Companies have to deal with huge amounts of heterogeneous information, usually stored in distributed datasets that make use of different data schemas. This topic is especially crucial for enterprises that deal with new and different kinds of business data as new services are provided; they need to be able to dynamically add new datasets with new schemas to their information systems. However, even though research efforts have been applied to deal with this integration problem, there is still a lack of practical approaches ready to be implemented for industrial cases. We present a web-based architecture and system built upon ontologies and other semantic web techniques to cope with federation of business data in real time. The scenario used to demonstrate the utility of the architecture is composed of actual data of a telecom company. Results show that our solution is more suitable, efficient and practical than other works. Copyright © 2014 John Wiley & Sons, Ltd.

In recent years, the task of automatically linking pieces of text (anchors) mentioned in a document to Wikipedia articles that represent the meaning of these anchors has received extensive research attention. Typically, link-to-Wikipedia systems try to find a set of Wikipedia articles that are candidates to represent the meaning of the anchor and, later, rank these candidates to select the most appropriate one. In this ranking process the systems rely on context information obtained from the document where the anchor is mentioned and/or from Wikipedia. In this paper we center our attention in the use of Wikipedia links as context information. In particular, we offer a review of several candidate ranking approaches in the state-of-the-art that rely on Wikipedia link information. In addition, we provide a comparative empirical evaluation of the different approaches on five different corpora: the TAC 2010 corpus and four corpora built from actual Wikipedia articles and news items.

Programming automated web navigation assistants, i.e., applications that automatically navigate the web performing specific tasks for the user, is far from easy. Since HTML pages offered by legacy web-based applications, which are designed to be manipulated only by people using browsers, web pages contain semi-structured information [P. Atzeni, et al., 1997] whose data schema can easily be changed, the creation and even the maintenance of this kind of applications, is very expensive. However, an increasing amount of information sources and online applications have been added to the web during the last few years, so assistants for automating tasks over those web-enabled applications are more and more needed. These assistants may automate tasks by filling in forms, following links, analyzing data embedded in web pages and performing computations over those data on behalf of the user. Software engineering techniques are clearly needed to reduce the cost, not just creating these programs (by significantly reducing their time-to-market), but even more importantly, maintaining them working properly, reducing the cost of readapting them to web site pages whose structure or navigation schemes are frequently changed. This paper proposes the well known formal method message sequence charts (MSC) [ITU-T, 1997] as a base for defining a language for programming web navigation assistants which may navigate a web site according to the user's aims. This specification language, called XPlore, is specially suited for both requirements engineering and automatic generation of an executable, and has been successfully tested on several well known web sites.

A formal refinement calculus targeted at system-level descriptions in the IEEE standard hardware description language VHDL is described here. Refinement can be used to develop hardware description code that is “correct by construction”. the calculus is closely related to a Hoare-style programming logic for VHDL and real-time systems in general. That logic and a semantics for a core subset of VHDL are described. The programming logic and the associated refinement calculus are shown to be complete. This means that if there is a code that can be shown to implement a given specification, then it will be derivable from the specification via the calculus.