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Publications

Publications by Vítor Francisco Fonte

2015

Concise server-wide causality management for eventually consistent data stores

Authors
Gonçalves, R; Almeida, PS; Baquero, C; Fonte, V;

Publication
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics)

Abstract
Large scale distributed data stores rely on optimistic replication to scale and remain highly available in the face of network partitions. Managing data without coordination results in eventually consistent data stores that allow for concurrent data updates. These systems often use anti-entropy mechanisms (like Merkle Trees) to detect and repair divergent data versions across nodes. However, in practice hash-based data structures are too expensive for large amounts of data and create too many false conflicts. Another aspect of eventual consistency is detecting write conflicts. Logical clocks are often used to track data causality, necessary to detect causally concurrent writes on the same key. However, there is a nonnegligible metadata overhead per key, which also keeps growing with time, proportional with the node churn rate. Another challenge is deleting keys while respecting causality: while the values can be deleted, perkey metadata cannot be permanently removed without coordination. We introduce a new causality management framework for eventually consistent data stores, that leverages node logical clocks (Bitmapped Version Vectors) and a new key logical clock (Dotted Causal Container) to provides advantages on multiple fronts: 1) a new efficient and lightweight anti-entropy mechanism; 2) greatly reduced per-key causality metadata size; 3) accurate key deletes without permanent metadata. © IFIP International Federation for Information Processing 2015.

2017

Promoting entrepreneurship among informatics engineering students: insights from a case study

Authors
Fernandes, JM; Afonso, P; Fonte, V; Alves, V; Ribeiro, AN;

Publication
EUROPEAN JOURNAL OF ENGINEERING EDUCATION

Abstract
Universities seek to promote entrepreneurship through effective education approaches, which need to be in permanent evolution. Nevertheless, the literature in entrepreneurship education lacks empirical evidence. This article discusses relevant issues related to promoting entrepreneurship in the software field, based on the experience of a 15-European Credit Transfer and Accumulation System course. This course seeks to instil in the students the recognition of the need to reconcile technical and business visions, organisational and commercial aspects, most of which have never been addressed previously. A series of semi-structured interviews made it possible to obtain relevant insights about the teaching-learning process underlying this course and its evolution over a seven-year period. Materials related with this course have been analysed, namely guidelines produced by the teachers and deliverables produced by the students. This article discusses the dimensions that were identified as fundamental for promoting entrepreneurship skills in the field of software, namely teamwork, project engagement, and contact with the market.

2017

DottedDB: Anti-Entropy without Merkle Trees, Deletes without Tombstones

Authors
Goncalves, R; Almeida, PS; Baquero, C; Fonte, V;

Publication
36th IEEE Symposium on Reliable Distributed Systems, SRDS 2017, Hong Kong, Hong Kong, September 26-29, 2017

Abstract

2014

Scalable and Accurate Causality Tracking for Eventually Consistent Stores

Authors
Sergio Almeida, PS; Baquero, C; Goncalves, R; Preguica, N; Fonte, V;

Publication
DISTRIBUTED APPLICATIONS AND INTEROPERABLE SYSTEMS (DAIS 2014)

Abstract
In cloud computing environments, data storage systems often rely on optimistic replication to provide good performance and availability even in the presence of failures or network partitions. In this scenario, it is important to be able to accurately and efficiently identify updates executed concurrently. Current approaches to causality tracking in optimistic replication have problems with concurrent updates: they either (1) do not scale, as they require replicas to maintain information that grows linearly with the number of writes or unique clients; (2) lose information about causality, either by removing entries from client-id based version vectors or using server-id based version vectors, which cause false conflicts. We propose a new logical clock mechanism and a logical clock framework that together support a traditional key-value store API, while capturing causality in an accurate and scalable way, avoiding false conflicts. It maintains concise information per data replica, only linear on the number of replica servers, and allows data replicas to be compared and merged linear with the number of replica servers and versions.

2018

Qualification offer in EGOV competencies in PALOP-TL

Authors
Silva, JMC; Ramos, LFM; Fonte, V;

Publication
ACM International Conference Proceeding Series

Abstract
Information and Communications Technologies (ICT) have been successfully used in order to promote and pursue the goals of UN's 2030 Agenda for Sustainable Development. Meeting these goals, however, require significant efforts on public policy development, adequate planning and implementation, as well as qualified human resources working at every level of government, public administration and institutions. This paper presents a first quantitative analysis originated from Electronic Government-related training sessions that took place on all five Portuguese Speaking African Countries, and in Timor-Leste along 2017. The results focus on (i) the availability of higher education institutions offering courses related to EGOV on each of those countries; (ii) the qualification of the professionals attending those sessions; and (iii) how availability of local higher education courses translates into qualifications of local professionals serving at public administration level. This paper also discusses some perceptions gathered from the field, both from participants and lecturer teams, framing additional challenges that EGOV-related courses must take into account in those particular settings. It concludes by pointing out some of the works already taking place, which provides a deeper understanding of the workforce competencies in EGOV for each of those countries. © 2018 Copyright is held by the owner/author(s). Publication rights licensed to ACM.

2019

Optimal Control Applied to an Irrigation Planning Problem : a real case study in Portugal

Authors
Lopes, SO; Pereira, RMS; Pereira, PA; Caldeira, AC; Fonte, VF;

Publication
International Journal of Hydrology Science and Technology

Abstract

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