15 Search Results for "Santos, Nuno"

Document
DOI: 10.4230/LIPIcs.ECOOP.2024.3
A Dynamic Logic for Symbolic Execution for the Smart Contract Programming Language Michelson

Authors: Barnabas Arvay, Thi Thu Ha Doan, and Peter Thiemann

Published in: LIPIcs, Volume 313, 38th European Conference on Object-Oriented Programming (ECOOP 2024)

Abstract
Verification of smart contracts is an important topic in the context of blockchain technology. We study an approach to verification that is based on symbolic execution. As a formal basis for symbolic execution, we design a dynamic logic for Michelson, the smart contract language of the Tezos blockchain, and prove its soundness in the proof assistant Agda. Towards the soundness proof we formalize the concrete semantics as well as its symbolic counterpart in a unified setting. The logic encompasses single contract runs as well as inter-contract runs chained in a single transaction.
Cite as

Barnabas Arvay, Thi Thu Ha Doan, and Peter Thiemann. A Dynamic Logic for Symbolic Execution for the Smart Contract Programming Language Michelson. In 38th European Conference on Object-Oriented Programming (ECOOP 2024). Leibniz International Proceedings in Informatics (LIPIcs), Volume 313, pp. 3:1-3:26, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@InProceedings{arvay_et_al:LIPIcs.ECOOP.2024.3,
  author =	{Arvay, Barnabas and Doan, Thi Thu Ha and Thiemann, Peter},
  title =	{{A Dynamic Logic for Symbolic Execution for the Smart Contract Programming Language Michelson}},
  booktitle =	{38th European Conference on Object-Oriented Programming (ECOOP 2024)},
  pages =	{3:1--3:26},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-341-6},
  ISSN =	{1868-8969},
  year =	{2024},
  volume =	{313},
  editor =	{Aldrich, Jonathan and Salvaneschi, Guido},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ECOOP.2024.3},
  URN =		{urn:nbn:de:0030-drops-208529},
  doi =		{10.4230/LIPIcs.ECOOP.2024.3},
  annote =	{Keywords: Smart Contract, Blockchain, Formal Verification, Symbolic Execution}
}
Document
DOI: 10.4230/LIPIcs.CP.2024.8
Slide&Drill, a New Approach for Multi-Objective Combinatorial Optimization

Authors: João Cortes, Inês Lynce, and Vasco Manquinho

Published in: LIPIcs, Volume 307, 30th International Conference on Principles and Practice of Constraint Programming (CP 2024)

Abstract
Following the successful use of Propositional Satisfiability (SAT) algorithms in Boolean optimization (e.g., Maximum Satisfiability), several SAT-based algorithms have been proposed for Multi-Objective Combinatorial Optimization (MOCO). However, these new algorithms either provide a small subset of the Pareto front or follow a more exploratory search procedure and the solutions found are usually distant from the Pareto front. We extend the state of the art with a new SAT-based MOCO solver, Slide and Drill (Slide&Drill), that hones an upper bound set of the exact solution. Moreover, we show that Slide&Drill neatly complements proposed UNSAT-SAT algorithms for MOCO. These algorithms can work in tandem over the same shared "blackboard" formula, in order to enable a faster convergence. Experimental results in several sets of benchmark instances show that Slide&Drill can outperform other SAT-based algorithms for MOCO, in particular when paired with previously proposed UNSAT-SAT algorithms.
Cite as

João Cortes, Inês Lynce, and Vasco Manquinho. Slide&Drill, a New Approach for Multi-Objective Combinatorial Optimization. In 30th International Conference on Principles and Practice of Constraint Programming (CP 2024). Leibniz International Proceedings in Informatics (LIPIcs), Volume 307, pp. 8:1-8:17, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@InProceedings{cortes_et_al:LIPIcs.CP.2024.8,
  author =	{Cortes, Jo\~{a}o and Lynce, In\^{e}s and Manquinho, Vasco},
  title =	{{Slide\&Drill, a New Approach for Multi-Objective Combinatorial Optimization}},
  booktitle =	{30th International Conference on Principles and Practice of Constraint Programming (CP 2024)},
  pages =	{8:1--8:17},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-336-2},
  ISSN =	{1868-8969},
  year =	{2024},
  volume =	{307},
  editor =	{Shaw, Paul},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.CP.2024.8},
  URN =		{urn:nbn:de:0030-drops-206932},
  doi =		{10.4230/LIPIcs.CP.2024.8},
  annote =	{Keywords: Multi-Objective Combinatorial Optimization, Satisfiability Algorithms}
}
Document
DOI: 10.4230/LIPIcs.WABI.2024.11
The mod-minimizer: A Simple and Efficient Sampling Algorithm for Long k-mers

Authors: Ragnar Groot Koerkamp and Giulio Ermanno Pibiri

Published in: LIPIcs, Volume 312, 24th International Workshop on Algorithms in Bioinformatics (WABI 2024)

Abstract
Motivation. Given a string S, a minimizer scheme is an algorithm defined by a triple (k,w,𝒪) that samples a subset of k-mers (k-long substrings) from a string S. Specifically, it samples the smallest k-mer according to the order 𝒪 from each window of w consecutive k-mers in S. Because consecutive windows can sample the same k-mer, the set of the sampled k-mers is typically much smaller than S. More generally, we consider substring sampling algorithms that respect a window guarantee: at least one k-mer must be sampled from every window of w consecutive k-mers. As a sampled k-mer is uniquely identified by its absolute position in S, we can define the density of a sampling algorithm as the fraction of distinct sampled positions. Good methods have low density which, by respecting the window guarantee, is lower bounded by 1/w. It is however difficult to design a sequence-agnostic algorithm with provably optimal density. In practice, the order 𝒪 is usually implemented using a pseudo-random hash function to obtain the so-called random minimizer. This scheme is simple to implement, very fast to compute even in streaming fashion, and easy to analyze. However, its density is almost a factor of 2 away from the lower bound for large windows. Methods. In this work we introduce mod-sampling, a two-step sampling algorithm to obtain new minimizer schemes. Given a (small) parameter t, the mod-sampling algorithm finds the position p of the smallest t-mer in a window. It then samples the k-mer at position pod w. The lr-minimizer uses t = k-w and the mod-minimizer uses t≡ k (mod w). Results. These new schemes have provably lower density than random minimizers and other schemes when k is large compared to w, while being as fast to compute. Importantly, the mod-minimizer achieves optimal density when k → ∞. Although the mod-minimizer is not the first method to achieve optimal density for large k, its proof of optimality is simpler than previous work. We provide pseudocode for a number of other methods and compare to them. In practice, the mod-minimizer has considerably lower density than the random minimizer and other state-of-the-art methods, like closed syncmers and miniception, when k > w. We plugged the mod-minimizer into SSHash, a k-mer dictionary based on minimizers. For default parameters (w,k) = (11,21), space usage decreases by 15% when indexing the whole human genome (GRCh38), while maintaining its fast query time.
Cite as

Ragnar Groot Koerkamp and Giulio Ermanno Pibiri. The mod-minimizer: A Simple and Efficient Sampling Algorithm for Long k-mers. In 24th International Workshop on Algorithms in Bioinformatics (WABI 2024). Leibniz International Proceedings in Informatics (LIPIcs), Volume 312, pp. 11:1-11:23, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@InProceedings{grootkoerkamp_et_al:LIPIcs.WABI.2024.11,
  author =	{Groot Koerkamp, Ragnar and Pibiri, Giulio Ermanno},
  title =	{{The mod-minimizer: A Simple and Efficient Sampling Algorithm for Long k-mers}},
  booktitle =	{24th International Workshop on Algorithms in Bioinformatics (WABI 2024)},
  pages =	{11:1--11:23},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-340-9},
  ISSN =	{1868-8969},
  year =	{2024},
  volume =	{312},
  editor =	{Pissis, Solon P. and Sung, Wing-Kin},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.WABI.2024.11},
  URN =		{urn:nbn:de:0030-drops-206552},
  doi =		{10.4230/LIPIcs.WABI.2024.11},
  annote =	{Keywords: Minimizers, Randomized algorithms, Sketching, Hashing}
}
Document
DOI: 10.4230/LIPIcs.ECOOP.2023.24
Toward Tool-Independent Summaries for Symbolic Execution

Authors: Frederico Ramos, Nuno Sabino, Pedro Adão, David A. Naumann, and José Fragoso Santos

Published in: LIPIcs, Volume 263, 37th European Conference on Object-Oriented Programming (ECOOP 2023)

Abstract
We introduce a new symbolic reflection API for implementing tool-independent summaries for the symbolic execution of C programs. We formalise the proposed API as a symbolic semantics and extend two state-of-the-art symbolic execution tools with support for it. Using the proposed API, we implement 67 tool-independent symbolic summaries for a total of 26 libc functions. Furthermore, we present SumBoundVerify, a fully automatic summary validation tool for checking the bounded correctness of the symbolic summaries written using our symbolic reflection API. We use SumBoundVerify to validate 37 symbolic summaries taken from 3 state-of-the-art symbolic execution tools, angr, Binsec and Manticore, detecting a total of 24 buggy summaries.
Cite as

Frederico Ramos, Nuno Sabino, Pedro Adão, David A. Naumann, and José Fragoso Santos. Toward Tool-Independent Summaries for Symbolic Execution. In 37th European Conference on Object-Oriented Programming (ECOOP 2023). Leibniz International Proceedings in Informatics (LIPIcs), Volume 263, pp. 24:1-24:29, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2023)

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@InProceedings{ramos_et_al:LIPIcs.ECOOP.2023.24,
  author =	{Ramos, Frederico and Sabino, Nuno and Ad\~{a}o, Pedro and Naumann, David A. and Fragoso Santos, Jos\'{e}},
  title =	{{Toward Tool-Independent Summaries for Symbolic Execution}},
  booktitle =	{37th European Conference on Object-Oriented Programming (ECOOP 2023)},
  pages =	{24:1--24:29},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-281-5},
  ISSN =	{1868-8969},
  year =	{2023},
  volume =	{263},
  editor =	{Ali, Karim and Salvaneschi, Guido},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ECOOP.2023.24},
  URN =		{urn:nbn:de:0030-drops-182171},
  doi =		{10.4230/LIPIcs.ECOOP.2023.24},
  annote =	{Keywords: Symbolic Execution, Runtime Modelling, Symbolic Summaries}
}
Document
Artifact
DOI: 10.4230/DARTS.9.2.7
Toward Tool-Independent Summaries for Symbolic Execution (Artifact)

Authors: Frederico Ramos, Nuno Sabino, Pedro Adão, David A. Naumann, and José Fragoso Santos

Published in: DARTS, Volume 9, Issue 2, Special Issue of the 37th European Conference on Object-Oriented Programming (ECOOP 2023)

Abstract
The artifact contains the extended versions of the tools angr and AVD with support for the symbolic reflection API proposed in the paper. Additionally, the artifact contains the source code of SumBoundVerify, our novel tool for the bounded-verification of symbolic summaries for the C programming language. The artifact contains all the scripts and datasets required to obtain the results presented in the paper, including: a library of 67 symbolic summaries implemented using the proposed symbolic reflection API; two symbolic test suites designed to test two open source C libraries; and the source code of the third-party summaries that were validated checked with SumBoundVerify.
Cite as

Frederico Ramos, Nuno Sabino, Pedro Adão, David A. Naumann, and José Fragoso Santos. Toward Tool-Independent Summaries for Symbolic Execution (Artifact). In Special Issue of the 37th European Conference on Object-Oriented Programming (ECOOP 2023). Dagstuhl Artifacts Series (DARTS), Volume 9, Issue 2, pp. 7:1-7:4, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2023)

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@Article{ramos_et_al:DARTS.9.2.7,
  author =	{Ramos, Frederico and Sabino, Nuno and Ad\~{a}o, Pedro and Naumann, David A. and Fragoso Santos, Jos\'{e}},
  title =	{{Toward Tool-Independent Summaries for Symbolic Execution (Artifact)}},
  pages =	{7:1--7:4},
  journal =	{Dagstuhl Artifacts Series},
  ISSN =	{2509-8195},
  year =	{2023},
  volume =	{9},
  number =	{2},
  editor =	{Ramos, Frederico and Sabino, Nuno and Ad\~{a}o, Pedro and Naumann, David A. and Fragoso Santos, Jos\'{e}},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/DARTS.9.2.7},
  URN =		{urn:nbn:de:0030-drops-182478},
  doi =		{10.4230/DARTS.9.2.7},
  annote =	{Keywords: Symbolic Execution, Runtime Modelling, Symbolic Summaries}
}
Document
DOI: 10.4230/OASIcs.SLATE.2022.9
Classification of Public Administration Complaints

Authors: Francisco Caldeira, Luís Nunes, and Ricardo Ribeiro

Published in: OASIcs, Volume 104, 11th Symposium on Languages, Applications and Technologies (SLATE 2022)

Abstract
Complaint management is a problem faced by many organizations that is both vital to customer image and highly dependent on human resources. This work attempts to tackle a part of the problem, by classifying summaries of complaints using machine learning models in order to better redirect these to the appropriate responders. The main challenges of this task is that training datasets are often small and highly imbalanced. This can can have a big impact on the performance of classification models. The dataset analyzed in this work suffers from both of these problems, being relatively small and having labels in different proportions. In this work, two different techniques are analyzed: combining classes together to increase the number of elements of the new class; and, providing new artificial examples for some classes via translation into other languages. The classification models explored were the following: k-NN, SVM, Naïve Bayes, boosting, and Deep Learning approaches, including transformers. The paper concludes that although, as expected, the classes with little representation are hard to classify, the techniques explored helped to boost the performance, especially in the classes with a low number of elements. SVM and BERT-based models outperformed their peers.
Cite as

Francisco Caldeira, Luís Nunes, and Ricardo Ribeiro. Classification of Public Administration Complaints. In 11th Symposium on Languages, Applications and Technologies (SLATE 2022). Open Access Series in Informatics (OASIcs), Volume 104, pp. 9:1-9:12, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2022)

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@InProceedings{caldeira_et_al:OASIcs.SLATE.2022.9,
  author =	{Caldeira, Francisco and Nunes, Lu{\'\i}s and Ribeiro, Ricardo},
  title =	{{Classification of Public Administration Complaints}},
  booktitle =	{11th Symposium on Languages, Applications and Technologies (SLATE 2022)},
  pages =	{9:1--9:12},
  series =	{Open Access Series in Informatics (OASIcs)},
  ISBN =	{978-3-95977-245-7},
  ISSN =	{2190-6807},
  year =	{2022},
  volume =	{104},
  editor =	{Cordeiro, Jo\~{a}o and Pereira, Maria Jo\~{a}o and Rodrigues, Nuno F. and Pais, Sebasti\~{a}o},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/OASIcs.SLATE.2022.9},
  URN =		{urn:nbn:de:0030-drops-167555},
  doi =		{10.4230/OASIcs.SLATE.2022.9},
  annote =	{Keywords: Text Classification, Natural Language Processing, Deep Learning, BERT}
}
Document
DOI: 10.4230/OASIcs.SLATE.2022.10
Comparing Different Approaches for Detecting Hate Speech in Online Portuguese Comments

Authors: Bernardo Cunha Matos, Raquel Bento Santos, Paula Carvalho, Ricardo Ribeiro, and Fernando Batista

Published in: OASIcs, Volume 104, 11th Symposium on Languages, Applications and Technologies (SLATE 2022)

Abstract
Online Hate Speech (OHS) has been growing dramatically on social media, which has motivated researchers to develop a diversity of methods for its automated detection. However, the detection of OHS in Portuguese is still little studied. To fill this gap, we explored different models that proved to be successful in the literature to address this task. In particular, we have explored transfer learning approaches, based on existing BERT-like pre-trained models. The performed experiments were based on CO-HATE, a corpus of YouTube comments posted by the Portuguese online community that was manually labeled by different annotators. Among other categories, those comments were labeled regarding the presence of hate speech and the type of hate speech, specifically overt and covert hate speech. We have assessed the impact of using annotations from different annotators on the performance of such models. In addition, we have analyzed the impact of distinguishing overt and and covert hate speech. The results achieved show the importance of considering the annotator’s profile in the development of hate speech detection models. Regarding the hate speech type, the results obtained do not allow to make any conclusion on what type is easier to detect. Finally, we show that pre-processing does not seem to have a significant impact on the performance of this specific task.
Cite as

Bernardo Cunha Matos, Raquel Bento Santos, Paula Carvalho, Ricardo Ribeiro, and Fernando Batista. Comparing Different Approaches for Detecting Hate Speech in Online Portuguese Comments. In 11th Symposium on Languages, Applications and Technologies (SLATE 2022). Open Access Series in Informatics (OASIcs), Volume 104, pp. 10:1-10:12, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2022)

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@InProceedings{matos_et_al:OASIcs.SLATE.2022.10,
  author =	{Matos, Bernardo Cunha and Santos, Raquel Bento and Carvalho, Paula and Ribeiro, Ricardo and Batista, Fernando},
  title =	{{Comparing Different Approaches for Detecting Hate Speech in Online Portuguese Comments}},
  booktitle =	{11th Symposium on Languages, Applications and Technologies (SLATE 2022)},
  pages =	{10:1--10:12},
  series =	{Open Access Series in Informatics (OASIcs)},
  ISBN =	{978-3-95977-245-7},
  ISSN =	{2190-6807},
  year =	{2022},
  volume =	{104},
  editor =	{Cordeiro, Jo\~{a}o and Pereira, Maria Jo\~{a}o and Rodrigues, Nuno F. and Pais, Sebasti\~{a}o},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/OASIcs.SLATE.2022.10},
  URN =		{urn:nbn:de:0030-drops-167560},
  doi =		{10.4230/OASIcs.SLATE.2022.10},
  annote =	{Keywords: Hate Speech, Text Classification, Transfer Learning, Supervised Learning, Deep Learning}
}
Document
DOI: 10.4230/OASIcs.SLATE.2022.11
Semi-Supervised Annotation of Portuguese Hate Speech Across Social Media Domains

Authors: Raquel Bento Santos, Bernardo Cunha Matos, Paula Carvalho, Fernando Batista, and Ricardo Ribeiro

Published in: OASIcs, Volume 104, 11th Symposium on Languages, Applications and Technologies (SLATE 2022)

Abstract
With the increasing spread of hate speech (HS) on social media, it becomes urgent to develop models that can help detecting it automatically. Typically, such models require large-scale annotated corpora, which are still scarce in languages such as Portuguese. However, creating manually annotated corpora is a very expensive and time-consuming task. To address this problem, we propose an ensemble of two semi-supervised models that can be used to automatically create a corpus representative of online hate speech in Portuguese. The first model combines Generative Adversarial Networks and a BERT-based model. The second model is based on label propagation, and consists of propagating labels from existing annotated corpora to the unlabeled data, by exploring the notion of similarity. We have explored the annotations of three existing corpora (CO-HATE, ToLR-BR, and HPHS) in order to automatically annotate FIGHT, a corpus composed of geolocated tweets produced in the Portuguese territory. Through the process of selecting the best model and the corresponding setup, we have tested different pre-trained embeddings, performed experiments using different training subsets, labeled by different annotators with different perspectives, and performed several experiments with active learning. Furthermore, this work explores back translation as a mean to automatically generate additional hate speech samples. The best results were achieved by combining all the labeled datasets, obtaining 0.664 F1-score for the Hate Speech class in FIGHT.
Cite as

Raquel Bento Santos, Bernardo Cunha Matos, Paula Carvalho, Fernando Batista, and Ricardo Ribeiro. Semi-Supervised Annotation of Portuguese Hate Speech Across Social Media Domains. In 11th Symposium on Languages, Applications and Technologies (SLATE 2022). Open Access Series in Informatics (OASIcs), Volume 104, pp. 11:1-11:14, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2022)

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@InProceedings{santos_et_al:OASIcs.SLATE.2022.11,
  author =	{Santos, Raquel Bento and Matos, Bernardo Cunha and Carvalho, Paula and Batista, Fernando and Ribeiro, Ricardo},
  title =	{{Semi-Supervised Annotation of Portuguese Hate Speech Across Social Media Domains}},
  booktitle =	{11th Symposium on Languages, Applications and Technologies (SLATE 2022)},
  pages =	{11:1--11:14},
  series =	{Open Access Series in Informatics (OASIcs)},
  ISBN =	{978-3-95977-245-7},
  ISSN =	{2190-6807},
  year =	{2022},
  volume =	{104},
  editor =	{Cordeiro, Jo\~{a}o and Pereira, Maria Jo\~{a}o and Rodrigues, Nuno F. and Pais, Sebasti\~{a}o},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/OASIcs.SLATE.2022.11},
  URN =		{urn:nbn:de:0030-drops-167570},
  doi =		{10.4230/OASIcs.SLATE.2022.11},
  annote =	{Keywords: Hate Speech, Semi-Supervised Learning, Semi-Automatic Annotation}
}
Document
DOI: 10.4230/OASIcs.SLATE.2022.12
Large Semantic Graph Summarization Using Namespaces

Authors: Ana Rita Santos Lopes da Costa, André Santos, and José Paulo Leal

Published in: OASIcs, Volume 104, 11th Symposium on Languages, Applications and Technologies (SLATE 2022)

Abstract
We propose an approach to summarize large semantics graphs using namespaces. Semantic graphs based on the Resource Description Framework (RDF) use namespaces on their serializations. Although these namespaces are not part of RDF semantics, they have intrinsic meaning. Based on this insight, we use namespaces to create summary graphs of reduced size, more amenable to be visualized. In the summarization, object literals are also reduced to their data type and the blank nodes to a group of their own. The visualization created for the summary graph aims to give insight of the original large graph. This paper describes the proposed approach and reports on the results obtained with representative large semantic graphs.
Cite as

Ana Rita Santos Lopes da Costa, André Santos, and José Paulo Leal. Large Semantic Graph Summarization Using Namespaces. In 11th Symposium on Languages, Applications and Technologies (SLATE 2022). Open Access Series in Informatics (OASIcs), Volume 104, pp. 12:1-12:9, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2022)

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@InProceedings{dacosta_et_al:OASIcs.SLATE.2022.12,
  author =	{da Costa, Ana Rita Santos Lopes and Santos, Andr\'{e} and Leal, Jos\'{e} Paulo},
  title =	{{Large Semantic Graph Summarization Using Namespaces}},
  booktitle =	{11th Symposium on Languages, Applications and Technologies (SLATE 2022)},
  pages =	{12:1--12:9},
  series =	{Open Access Series in Informatics (OASIcs)},
  ISBN =	{978-3-95977-245-7},
  ISSN =	{2190-6807},
  year =	{2022},
  volume =	{104},
  editor =	{Cordeiro, Jo\~{a}o and Pereira, Maria Jo\~{a}o and Rodrigues, Nuno F. and Pais, Sebasti\~{a}o},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/OASIcs.SLATE.2022.12},
  URN =		{urn:nbn:de:0030-drops-167585},
  doi =		{10.4230/OASIcs.SLATE.2022.12},
  annote =	{Keywords: Semantic graph, RDF, namespaces, reification}
}
Document
DOI: 10.4230/OASIcs.SLATE.2022.13
Metaobject Protocols for Julia

Authors: Marcelo Santos and António Menezes Leitão

Published in: OASIcs, Volume 104, 11th Symposium on Languages, Applications and Technologies (SLATE 2022)

Abstract
Metaobject Protocols enable programmers to extend programming languages without the need to understand the lower level details of their implementation. However, designing these protocols comes with two challenges: allow programmers to limit their concerns to higher level concepts and minimize performance penalties in programs. In this work, we propose metaobject protocol for the programming language Julia. Julia’s object system is very limited, when compared to languages following the Object-Oriented paradigm. However, Julia’s compilation approach allows for a considerable degree of code optimization through the exploration of runtime type information. Through the usage of Julia’s run-time optimizations, we propose a metaobject protocol that combines user-extensibility with limited performance penalties. This paper focuses on the development of a multiple inheritance method dispatch and method combination mechanisms with zero runtime overhead.
Cite as

Marcelo Santos and António Menezes Leitão. Metaobject Protocols for Julia. In 11th Symposium on Languages, Applications and Technologies (SLATE 2022). Open Access Series in Informatics (OASIcs), Volume 104, pp. 13:1-13:15, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2022)

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@InProceedings{santos_et_al:OASIcs.SLATE.2022.13,
  author =	{Santos, Marcelo and Leit\~{a}o, Ant\'{o}nio Menezes},
  title =	{{Metaobject Protocols for Julia}},
  booktitle =	{11th Symposium on Languages, Applications and Technologies (SLATE 2022)},
  pages =	{13:1--13:15},
  series =	{Open Access Series in Informatics (OASIcs)},
  ISBN =	{978-3-95977-245-7},
  ISSN =	{2190-6807},
  year =	{2022},
  volume =	{104},
  editor =	{Cordeiro, Jo\~{a}o and Pereira, Maria Jo\~{a}o and Rodrigues, Nuno F. and Pais, Sebasti\~{a}o},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/OASIcs.SLATE.2022.13},
  URN =		{urn:nbn:de:0030-drops-167597},
  doi =		{10.4230/OASIcs.SLATE.2022.13},
  annote =	{Keywords: Julia, Metaobject Protocols, Object-Oriented Programming, Performance}
}
Document
DOI: 10.4230/OASIcs.ICPEC.2022.2
Sprinter: A Didactic Linter for Structured Programming

Authors: Francisco Alfredo, André L. Santos, and Nuno Garrido

Published in: OASIcs, Volume 102, Third International Computer Programming Education Conference (ICPEC 2022)

Abstract
Code linters are tools for detecting improper uses of programming constructs and violations of style issues. Despite that professional linters are available for numerous languages, they are not targeted to introductory programming, given their prescriptive nature that does not take into consideration a didactic viewpoint of learning programming fundamentals. We present Sprinter, a didactic code linter for structured programming supporting Java whose novelty aspects are twofold: (a) providing formative feedback on code with comprehensive explanatory messages (rather then prescriptive); (b) capability of detecting some control-flow issues to a deeper extent than professional linters. We review Sprinter features against popular tools, namely IntelliJ IDEA and Sonarlint.
Cite as

Francisco Alfredo, André L. Santos, and Nuno Garrido. Sprinter: A Didactic Linter for Structured Programming. In Third International Computer Programming Education Conference (ICPEC 2022). Open Access Series in Informatics (OASIcs), Volume 102, pp. 2:1-2:8, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2022)

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@InProceedings{alfredo_et_al:OASIcs.ICPEC.2022.2,
  author =	{Alfredo, Francisco and Santos, Andr\'{e} L. and Garrido, Nuno},
  title =	{{Sprinter: A Didactic Linter for Structured Programming}},
  booktitle =	{Third International Computer Programming Education Conference (ICPEC 2022)},
  pages =	{2:1--2:8},
  series =	{Open Access Series in Informatics (OASIcs)},
  ISBN =	{978-3-95977-229-7},
  ISSN =	{2190-6807},
  year =	{2022},
  volume =	{102},
  editor =	{Sim\~{o}es, Alberto and Silva, Jo\~{a}o Carlos},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/OASIcs.ICPEC.2022.2},
  URN =		{urn:nbn:de:0030-drops-166063},
  doi =		{10.4230/OASIcs.ICPEC.2022.2},
  annote =	{Keywords: structured programming, code quality, code linter}
}
Document
Artifact
DOI: 10.4230/DARTS.8.2.20
Concolic Execution for WebAssembly (Artifact)

Authors: Filipe Marques, José Fragoso Santos, Nuno Santos, and Pedro Adão

Published in: DARTS, Volume 8, Issue 2, Special Issue of the 36th European Conference on Object-Oriented Programming (ECOOP 2022)

Abstract
This artifact contains the implementation of WASP, a symbolic execution engine for Wasm, and WASP-C, a symbolic execution framework for testing C programs built using WASP . WASP works directly on Wasm code and was built on top of a standard-compliant Wasm reference implementation [Andreas Haas et al., 2017]. WASP was thoroughly evaluated: it was used to symbolically test a generic data-structure library and the Amazon Encryption SDK for C, demonstrating that it can find bugs and generate high-coverage testing inputs for real-world C applications; WASP was further tested against the Test-Comp benchmark, obtaining results comparable to well-established symbolic execution and testing tools for C.
Cite as

Filipe Marques, José Fragoso Santos, Nuno Santos, and Pedro Adão. Concolic Execution for WebAssembly (Artifact). In Special Issue of the 36th European Conference on Object-Oriented Programming (ECOOP 2022). Dagstuhl Artifacts Series (DARTS), Volume 8, Issue 2, pp. 20:1-20:3, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2022)

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@Article{marques_et_al:DARTS.8.2.20,
  author =	{Marques, Filipe and Fragoso Santos, Jos\'{e} and Santos, Nuno and Ad\~{a}o, Pedro},
  title =	{{Concolic Execution for WebAssembly (Artifact)}},
  pages =	{20:1--20:3},
  journal =	{Dagstuhl Artifacts Series},
  ISSN =	{2509-8195},
  year =	{2022},
  volume =	{8},
  number =	{2},
  editor =	{Marques, Filipe and Fragoso Santos, Jos\'{e} and Santos, Nuno and Ad\~{a}o, Pedro},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/DARTS.8.2.20},
  URN =		{urn:nbn:de:0030-drops-162181},
  doi =		{10.4230/DARTS.8.2.20},
  annote =	{Keywords: Concolic Testing, WebAssembly, Test-Generation, Testing C Programs}
}
Document
DOI: 10.4230/LIPIcs.ECOOP.2022.11
Concolic Execution for WebAssembly

Authors: Filipe Marques, José Fragoso Santos, Nuno Santos, and Pedro Adão

Published in: LIPIcs, Volume 222, 36th European Conference on Object-Oriented Programming (ECOOP 2022)

Abstract
WebAssembly (Wasm) is a new binary instruction format that allows targeted compiled code written in high-level languages to be executed by the browser’s JavaScript engine with near-native speed. Despite its clear performance advantages, Wasm opens up the opportunity for bugs or security vulnerabilities to be introduced into Web programs, as pre-existing issues in programs written in unsafe languages can be transferred down to cross-compiled binaries. The source code of such binaries is frequently unavailable for static analysis, creating the demand for tools that can directly tackle Wasm code. Despite this potentially security-critical situation, there is still a noticeable lack of tool support for analysing Wasm binaries. We present WASP, a symbolic execution engine for testing Wasm modules, which works directly on Wasm code and was built on top of a standard-compliant Wasm reference implementation. WASP was thoroughly evaluated: it was used to symbolically test a generic data-structure library for C and the Amazon Encryption SDK for C, demonstrating that it can find bugs and generate high-coverage testing inputs for real-world C applications; and was further tested against the Test-Comp benchmark, obtaining results comparable to well-established symbolic execution and testing tools for C.
Cite as

Filipe Marques, José Fragoso Santos, Nuno Santos, and Pedro Adão. Concolic Execution for WebAssembly. In 36th European Conference on Object-Oriented Programming (ECOOP 2022). Leibniz International Proceedings in Informatics (LIPIcs), Volume 222, pp. 11:1-11:29, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2022)

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@InProceedings{marques_et_al:LIPIcs.ECOOP.2022.11,
  author =	{Marques, Filipe and Fragoso Santos, Jos\'{e} and Santos, Nuno and Ad\~{a}o, Pedro},
  title =	{{Concolic Execution for WebAssembly}},
  booktitle =	{36th European Conference on Object-Oriented Programming (ECOOP 2022)},
  pages =	{11:1--11:29},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-225-9},
  ISSN =	{1868-8969},
  year =	{2022},
  volume =	{222},
  editor =	{Ali, Karim and Vitek, Jan},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ECOOP.2022.11},
  URN =		{urn:nbn:de:0030-drops-162394},
  doi =		{10.4230/LIPIcs.ECOOP.2022.11},
  annote =	{Keywords: Concolic Testing, WebAssembly, Test-Generation, Testing C Programs}
}
Document
DOI: 10.4230/OASIcs.ATMOS.2018.2
Large Scale Railway Renewal Planning with a Multiobjective Modeling Approach

Authors: Nuno Sousa, Luis Alçada-Almeida, and João Coutinho-Rodrigues

Published in: OASIcs, Volume 65, 18th Workshop on Algorithmic Approaches for Transportation Modelling, Optimization, and Systems (ATMOS 2018)

Abstract
A multiobjective modeling approach for managing large scale railway infrastructure asset renewal is presented. An optimized intervention project schedule is obtained considering operational constraints in a three objectives model: evenly spreading investment throughout multiple years, minimizing total cost, minimizing work start postponements on higher priority railway sections. The MILP model was based on a real world case study; the objectives and constraints specified by an infrastructure management company. Results show that investment spreading greatly influences the other objectives and that total cost fluctuations depend on the overall condition of the railway infrastructure. The model can produce exact efficient solutions in reasonable time, even for very large-sized instances (a test network of similar size to the USA railway network, the largest in the world). The modeling approach is therefore a very useful, practical methodology, for generating optimized solutions and analyzing trade-offs among objectives, easing the task of ultimately selecting a solution and produce the works schedule for field implementation.
Cite as

Nuno Sousa, Luis Alçada-Almeida, and João Coutinho-Rodrigues. Large Scale Railway Renewal Planning with a Multiobjective Modeling Approach. In 18th Workshop on Algorithmic Approaches for Transportation Modelling, Optimization, and Systems (ATMOS 2018). Open Access Series in Informatics (OASIcs), Volume 65, pp. 2:1-2:9, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2018)

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@InProceedings{sousa_et_al:OASIcs.ATMOS.2018.2,
  author =	{Sousa, Nuno and Al\c{c}ada-Almeida, Luis and Coutinho-Rodrigues, Jo\~{a}o},
  title =	{{Large Scale Railway Renewal Planning with a Multiobjective Modeling Approach}},
  booktitle =	{18th Workshop on Algorithmic Approaches for Transportation Modelling, Optimization, and Systems (ATMOS 2018)},
  pages =	{2:1--2:9},
  series =	{Open Access Series in Informatics (OASIcs)},
  ISBN =	{978-3-95977-096-5},
  ISSN =	{2190-6807},
  year =	{2018},
  volume =	{65},
  editor =	{Bornd\"{o}rfer, Ralf and Storandt, Sabine},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/OASIcs.ATMOS.2018.2},
  URN =		{urn:nbn:de:0030-drops-97071},
  doi =		{10.4230/OASIcs.ATMOS.2018.2},
  annote =	{Keywords: Rail infrastructure, Renewal maintenance, Multiobjective modeling}
}
Document
DOI: 10.4230/LIPIcs.ICLP.2012.381
A Logic Programming approach for Access Control over RDF

Authors: Nuno Lopes, Sabrina Kirrane, Antoine Zimmermann, Axel Polleres, and Alessandra Mileo

Published in: LIPIcs, Volume 17, Technical Communications of the 28th International Conference on Logic Programming (ICLP'12) (2012)

Abstract
The Resource Description Framework (RDF) is an interoperable data representation format suitable for interchange and integration of data, especially in Open Data contexts. However, RDF is also becoming increasingly attractive in scenarios involving sensitive data, where data protection is a major concern. At its core, RDF does not support any form of access control and current proposals for extending RDF with access control do not fit well with the RDF representation model. Considering an enterprise scenario, we present a modelling that caters for access control over the stored RDF data in an intuitive and transparent manner. For this paper we rely on Annotated RDF, which introduces concepts from Annotated Logic Programming into RDF. Based on this model of the access control annotation domain, we propose a mechanism to manage permissions via application-specific logic rules. Furthermore, we illustrate how our Annotated Query Language (AnQL) provides a secure way to query this access control annotated RDF data.
Cite as

Nuno Lopes, Sabrina Kirrane, Antoine Zimmermann, Axel Polleres, and Alessandra Mileo. A Logic Programming approach for Access Control over RDF. In Technical Communications of the 28th International Conference on Logic Programming (ICLP'12). Leibniz International Proceedings in Informatics (LIPIcs), Volume 17, pp. 381-392, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2012)

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@InProceedings{lopes_et_al:LIPIcs.ICLP.2012.381,
  author =	{Lopes, Nuno and Kirrane, Sabrina and Zimmermann, Antoine and Polleres, Axel and Mileo, Alessandra},
  title =	{{A Logic Programming approach for Access Control over RDF}},
  booktitle =	{Technical Communications of the 28th International Conference on Logic Programming (ICLP'12)},
  pages =	{381--392},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-939897-43-9},
  ISSN =	{1868-8969},
  year =	{2012},
  volume =	{17},
  editor =	{Dovier, Agostino and Santos Costa, V{\'\i}tor},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ICLP.2012.381},
  URN =		{urn:nbn:de:0030-drops-36384},
  doi =		{10.4230/LIPIcs.ICLP.2012.381},
  annote =	{Keywords: Logic Programming, Annotation, Access Control, RDF}
}
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