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See detailAvoiding 5/4-powers on the alphabet of nonnegative integers (extended abstract)
Rowland, Eric; Stipulanti, Manon ULiege

in Lecture Notes in Computer Science (2020), 12086

We identify the structure of the lexicographically least word avoiding 5/4-powers on the alphabet of nonnegative integers.

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See detailRevisiting the Product Configuration Systems Development Procedure for Scrum Compliance: An i* Driven Process Fragment
Wautelet, Yves; Shafiee, Sara; Heng, Samedi ULiege

in Lecture Notes in Computer Science (2019, November)

Product Configuration Systems (PCS) are software applications supporting the design of products tailored to the individual desiderata of customers. PCS development does not follow the same procedure as ... [more ▼]

Product Configuration Systems (PCS) are software applications supporting the design of products tailored to the individual desiderata of customers. PCS development does not follow the same procedure as traditional software: indeed, due to its nature, specific knowledge needs to be collected, a set of custom engineering stages have thus been built-up. Within these stages, special requirements representation and design artifacts are used notably to deal with features inter-dependencies. More specifically, the Product Variant Master (PVM) has been specifically created for PCS knowledge representation while ClassResponsibility-Collaboration (CRC) cards and a UML Class Diagram are often indispensable for PCS object-oriented design. PCS development projects have gradually started to use agile methods like the Scrum. This paper presents a process fragment for conducting PCS development projects with Scrum; it overviews how the development team of a specific organization adapted the agile process to the PCS context. This process fragment has indeed been built on the basis of practitioners knowledge collected through 5 qualitative interviews (inductive approach) and exhaustively depict the activities performed by the team on PCS development projects of various size and context. Because of the possibility to represent social (role) dependencies, the fragment is visually represented using an i* Strategic Rationale Diagram. The main contribution of the paper is the fragment itself, it is intended to be dynamically used as an initial guidance for PCS development teams willing to conduct projects using Scrum; it can be tailored to any project/sprint and enriched at will. [less ▲]

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See detailTemplates for the k-binomial complexity of the Tribonacci word
Lejeune, Marie ULiege; Rigo, Michel ULiege; Rosenfeld, Matthieu ULiege

in Lecture Notes in Computer Science (2019, September), 11682

Consider k-binomial equivalence: two finite words are equivalent if they share the same subwords of length at most k with the same multiplicities. With this relation, the k-binomial complexity of an ... [more ▼]

Consider k-binomial equivalence: two finite words are equivalent if they share the same subwords of length at most k with the same multiplicities. With this relation, the k-binomial complexity of an infinite word 𝐱 maps the integer n to the number of pairwise non-equivalent factors of length n occurring in 𝐱. In this paper based on the notion of template introduced by Currie et al., we show that, for all 𝑘≥2, the k-binomial complexity of the Tribonacci word coincides with its usual factor complexity 𝑝(𝑛)=2𝑛+1. A similar result was already known for Sturmian words, but the proof relies on completely different techniques that seemingly could not be applied for Tribonacci. [less ▲]

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See detailComputing the k-binomial complextiy of the Thue-Morse word
Lejeune, Marie ULiege; Leroy, Julien ULiege; Rigo, Michel ULiege

in Lecture Notes in Computer Science (2019), 11647

Two finite words are k-binomially equivalent whenever they share the same subwords, i.e., subsequences, of length at most k with the same multiplicities. This is a refinement of both abelian equivalence ... [more ▼]

Two finite words are k-binomially equivalent whenever they share the same subwords, i.e., subsequences, of length at most k with the same multiplicities. This is a refinement of both abelian equivalence and the Simon congruence. The k-binomial complexity of an infinite word 𝐱 maps the integer n to the number of classes in the quotient, by this k-binomial equivalence relation, of the set of factors of length n occurring in 𝐱. This complexity measure has not been investigated very much. In this paper, we characterize the k-binomial complexity of the Thue–Morse word. The result is striking, compared to more familiar complexity functions. Although the Thue–Morse word is aperiodic, its k-binomial complexity eventually takes only two values. In this paper, we first express the number of occurrences of subwords appearing in iterates of the form 𝛹^ℓ(𝑤) for an arbitrary morphism 𝛹. We also thoroughly describe the factors of the Thue–Morse word by introducing a relevant new equivalence relation. [less ▲]

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See detailRecurrence in multidimensional words
Charlier, Emilie ULiege; Puzynina, Svetlana; Vandomme, Elise ULiege

in Lecture Notes in Computer Science (2019), 11417

In this paper we study various modifications of the notion of uniform recurrence in multidimensional infinite words. A d-dimensional infinite word is said to be uniformly recurrent if for each prefix ... [more ▼]

In this paper we study various modifications of the notion of uniform recurrence in multidimensional infinite words. A d-dimensional infinite word is said to be uniformly recurrent if for each prefix, there exists a fixed size such that each block of this size contains the prefix. We introduce and study a new notion of uniform recurrence of multidimensional infinite words: for each rational slope, each rectangular prefix must occur along this slope with bounded gaps. Such words are called uniformly recurrent along all directions. We provide several constructions of multidimensional infinite words satisfying this condition, and more generally, a series of three conditions on recurrence. We study general properties of these new notions and in particular we study the strong uniform recurrence of fixed points of square morphisms. [less ▲]

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See detailAgile Manifesto and Practices Selection for Tailoring Software Development: A Systematic Literature Review
Kiv, Soreangsey; Heng, Samedi ULiege; Kolp, Manuel et al

in Lecture Notes in Computer Science (2018, November), 11271

Agile methods have been largely used for many years to provide developers with a flexible software development process leading to software quality improvement. To get the best results and eliminate ... [more ▼]

Agile methods have been largely used for many years to provide developers with a flexible software development process leading to software quality improvement. To get the best results and eliminate unnecessary efforts, the development team should select the most appropriate methods and techniques. The fundamental core of an agile method has to be well-understood before deciding which parts of the method need to be adopted. We believe that the quickest way to do so is to understand the prescripts of the Agile Manifesto. Many researches have proposed different tailoring approaches based on the relation and straight-forward interpretation between each agile practice and agile values or principles. We however have observed that agile practitioners do not dedicate the necessary attention to the Agile Manifesto before adopting agile methods or practices and directly use them. It is because the importance of Agile Manifesto in tailoring context is not obvious enough to the community. This study aims at doing a systematic literature review on the existing case studies, to verify the relation between the Agile Manifesto and agile practice selection. [less ▲]

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See detailOn Modelers Ability to Build a Visual Diagram from a User Story Set: A Goal-Oriented Approach
Wautelet, Yves; Velghe, Mattijs; Heng, Samedi ULiege et al

in Lecture Notes in Computer Science (2018, March), 10753

[Context and Motivation] User Stories (US) are often used as requirement representation artifacts within agile projects. Within US sets, the nature, granularity and inter-dependencies of the elements ... [more ▼]

[Context and Motivation] User Stories (US) are often used as requirement representation artifacts within agile projects. Within US sets, the nature, granularity and inter-dependencies of the elements constituting each US is not or poorly represented. To deal with these drawbacks, previous research allowed to build a unified model for tagging the elements of the WHO, WHAT and WHY dimensions of a US; each tag representing a concept with an inherent nature and defined granularity. Once tagged, the US elements can be graphically represented with an icon and the modeler can define the inter-dependencies between the elements to build one or more so-called Rationale Trees (RT). [Question/Problem] RT and their benefits have been illustrated on case studies but the ability to easily build a RT in a genuine case for software modelers not familiar with the concepts needs to be evaluated. [Principal ideas/results] This paper presents the result of a double exercise aimed to evaluate how well novice and experienced modelers were able to build a RT out of an existing US set. The experiment explicitly forces the test subjects to attribute a concept to US elements and to link these together. [Contribution] On the basis of the conducted exper- iment, we highlight the encountered difficulties that the lambda modeler faces when building a RT with basic support. Overall, the test subjects have produced models of satisfying quality. Also, we highlight these necessary conditions that need to be provided to the lambda modeler to build a consistent RT. [less ▲]

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See detailDeep neural networks for automatic classification of anesthetic-induced unconsciousness
Patlatzoglou, K.; Chennu, S.; Boly, Mélanie et al

in Lecture Notes in Computer Science (2018), 11309 LNAI

Despite the common use of anesthetics to modulate consciousness in the clinic, brain-based monitoring of consciousness is uncommon. We combined electroencephalographic measurement of brain activity with ... [more ▼]

Despite the common use of anesthetics to modulate consciousness in the clinic, brain-based monitoring of consciousness is uncommon. We combined electroencephalographic measurement of brain activity with deep neural networks to automatically discriminate anesthetic states induced by propofol. Our results with leave-one-participant-out-cross-validation show that convolutional neural networks significantly outperform multilayer perceptrons in discrimination accuracy when working with raw time series. Perceptrons achieved comparable accuracy when provided with power spectral densities. These findings highlight the potential of deep convolutional networks for completely automatic extraction of useful spatio-temporo-spectral features from human EEG. © 2018, Springer Nature Switzerland AG. [less ▲]

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See detailFully leafed induced subtrees
Blondin Massé, Alexandre; De Carufel, Julien; Goupil, Alain et al

in Lecture Notes in Computer Science (2018), 10979

We consider the problem LIS of deciding whether there exists an induced subtree with exactly 𝑖≤𝑛 vertices and ℓ leaves in a given graph G with n vertices. We study the associated optimization problem ... [more ▼]

We consider the problem LIS of deciding whether there exists an induced subtree with exactly 𝑖≤𝑛 vertices and ℓ leaves in a given graph G with n vertices. We study the associated optimization problem, that consists in computing the maximal number of leaves, denoted by 𝐿𝐺(𝑖), realized by an induced subtree with i vertices, for 0≤𝑖≤𝑛. We begin by proving that the LIS problem is NP-complete in general. Then, we describe a nontrivial branch and bound algorithm that computes the function 𝐿𝐺 for any simple graph G. In the special case where G is a tree of maximum degree 𝛥, we provide a O(𝛥𝑛^3) time and O(𝑛^2) space algorithm to compute the function 𝐿𝐺. [less ▲]

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See detailEfficient Symbolic Representation of Convex Polyhedra in High-Dimensional Spaces
Boigelot, Bernard ULiege; Mainz, Isabelle ULiege

in Lecture Notes in Computer Science (2018)

This work is aimed at developing an efficient data structure for representing symbolically convex polyhedra. We introduce an original data structure, the Decomposed Convex Polyhedron (DCP), that is closed ... [more ▼]

This work is aimed at developing an efficient data structure for representing symbolically convex polyhedra. We introduce an original data structure, the Decomposed Convex Polyhedron (DCP), that is closed under intersection and linear transformations, and allows to check inclusion, equality, and emptiness. The main feature of DCPs lies in their ability to represent concisely polyhedra that can be expressed as combinations of simpler sets, which can overcome combinatorial explosion in high dimensional spaces. DCPs also have the advantage of being reducible into a canonical form, which makes them efficient for representing simple sets constructed by long sequences of manipulations, such as those handled by state-space exploration tools. Their practical efficiency has been evaluated with the help of a prototype implementation, with promising results. [less ▲]

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See detailMultivariate functional network connectivity for disorders of consciousness
Rudas, Jorge; Martínez, Darwin; Demertzi, Athina ULiege et al

in Lecture Notes in Computer Science (2017), 10125 LNCS

Recent evidence suggests that healthy brain is organized on large-scale spatially distant brain regions, which are temporally synchronized. These regions are known as resting state networks (RSNs). The ... [more ▼]

Recent evidence suggests that healthy brain is organized on large-scale spatially distant brain regions, which are temporally synchronized. These regions are known as resting state networks (RSNs). The level of interaction among these functional entities has been studied in the so called functional network connectivity (FNC). FNC aims to quantify the level of interaction between pairs of RSNs, which commonly emerge at similar spatial scale. Nevertheless, the human brain is a complex functional structure which is partitioned into functional regions that emerge at multiple spatial scales. In this work, we propose a novel multivariate FNC strategy to study interactions among communities of RSNs, these communities may emerge at different spatial scales. For this, first a community or hyperedge detection strategy was used to conform groups of RSNs with a similar behavior. Following, a distance correlation measurement was employed to quantify the level of interaction between these communities. The proposed strategy was evaluated in the characterization of patients with disorders of consciousness, a highly challenging problem in the clinical setting. The results suggest that the proposed strategy may improve the capacity of characterization of these brain altered conditions. [less ▲]

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See detailSustainability of users' commitment to Collaborative Design Tasks: an exploratory research
Elsen, Catherine ULiege; Vigneron, Lara ULiege; Acconcia, Alessandro ULiege et al

in Lecture Notes in Computer Science (2017), 10451

This paper investigates why end-users sometimes find difficult to fully invest themselves in a Living Lab initiative, at least on the long run. The paper builds insights on the basis of users’ feedback ... [more ▼]

This paper investigates why end-users sometimes find difficult to fully invest themselves in a Living Lab initiative, at least on the long run. The paper builds insights on the basis of users’ feedback about four projects currently managed by the Wallonia e-health Living Lab (WeLL) and pave the way for renewed models of interaction that could lead to sustainable satisfaction and commitment of end-users. [less ▲]

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See detailBridging User Story Sets with the Use Case Model
Wautelet, Yves; Heng, Samedi ULiege; Hintea, Diana et al

in Lecture Notes in Computer Science (2016, November), 9975

User Stories (US) are mostly used as basis for representing requirements in agile development. Written in a direct manner, US fail in producing a visual representation of the main system-to-be functions ... [more ▼]

User Stories (US) are mostly used as basis for representing requirements in agile development. Written in a direct manner, US fail in producing a visual representation of the main system-to-be functions. A Use-Case Diagram (UCD), on the other hand, intends to provide such a view. Approaches that map US sets to a UCD have been proposed; they however consider every US as a Use Case (UC). Nevertheless, a valid UC should not be an atomic task or a sub-process but enclose an entire scenario of the system use instead. A unified model of US templates to tag US sets was previously build. Within functional elements, it notably distinguishes granularity levels. In this paper, we propose to transform specific elements of a US set into a UCD using the granularity information obtained through tagging. In practice, such a transformation involves continuous round-tripping between the US and UC views; a CASE-tool supports this. [less ▲]

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See detailBCIs for DOC patients: Assessment, communication, and new directions
Ortner, R.; Annen, Jitka ULiege; Oertzen, T. V. et al

in Lecture Notes in Computer Science (2016), 9738

Recent work has sought to extend brain-computer interface (BCI) technology to persons diagnosed with a disorder of consciousness (DOC). This new approach can use real-time measures of brain activity to ... [more ▼]

Recent work has sought to extend brain-computer interface (BCI) technology to persons diagnosed with a disorder of consciousness (DOC). This new approach can use real-time measures of brain activity to facilitate assessment of conscious awareness, and potentially provide communication for some users. We present the mindBEAGLE system, a hardware and platform for these goals, results from two patients, and future directions. © Springer International Publishing Switzerland 2016. [less ▲]

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See detailA Brief History of MPLS Usage in IPv6
Vanaubel, Yves ULiege; Mérindol, Pascal; Pansiot, Jean-Jacques et al

in Lecture Notes in Computer Science (2016)

Recent researches have stated the fast deployment of IPv6. It has been demonstrated that IPv6 grows much faster, being so more and more adopted by both Internet service providers but also by servers and ... [more ▼]

Recent researches have stated the fast deployment of IPv6. It has been demonstrated that IPv6 grows much faster, being so more and more adopted by both Internet service providers but also by servers and end-hosts. In parallel, researches have been conducted to discover and assess the usage of MPLS tunnels. Indeed, recent developments in the ICMP protocol make certain categories of MPLS tunnels transparent to traceroute probing. However, these studies focus only on IPv4, where MPLS is strongly deployed. In this paper, we provide a first look at how MPLS is used under IPv6 networks using traceroute data collected by CAIDA. At first glance, we observe that the MPLS deployment and usage seem to greatly differ between IPv4 and IPv6, in particular in the way MPLS label stacks are used. While label stacks with at least two labels are marginal in IPv4 (and mostly correspond to a VPN usage), they are prevalent in IPv6. After a deeper analysis of the label stack typical content in IPv6, we show that such tunnels result from the use of 6PE. This is not really surprising since this mechanism was specifically designed to forward IPv6 traffic using MPLS tunnels through networks that are not fully IPv6 compliant. However, we show that it does not result from non dual-stack routers but rather from the absence of native IPv6 MPLS signaling protocols. Finally, we investigate a large Tier-1 network, Cogent, that stands out with an original set-up. [less ▲]

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See detailPermutations and shifts
Charlier, Emilie ULiege

in Lecture Notes in Computer Science (2016), 9840

The entropy of a symbolic dynamical system is usually defined in terms of the growth rate of the number of distinct allowed factors of length $n$. Bandt, Keller and Pompe showed that, for piecewise ... [more ▼]

The entropy of a symbolic dynamical system is usually defined in terms of the growth rate of the number of distinct allowed factors of length $n$. Bandt, Keller and Pompe showed that, for piecewise monotone interval maps, the entropy is also given by the number of permutations defined by consecutive elements in the trajectory of a point. This result is the starting point of several works of Elizalde where he investigates permutations in shift systems, notably in full shifts and in beta-shifts. The goal of this talk is to survey Elizalde's results. I will end by mentioning the case of negative beta-shifts, which has been simultaneously studied by Elizalde and Moore on the one hand, and by Steiner and myself on the other hand. [less ▲]

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See detailAn Econometric Analysis of Homeownership Determinants in Belgium
Xhignesse, Guillaume ULiege; Bianchet, Bruno ULiege; Cools, Mario ULiege et al

in Lecture Notes in Computer Science (2014, July), 8581

In market economies, homeownership is associated with positive ex- ternalities. Increasing the levels of homeownership has been an objective of governments for the last decades. The analysis of the ... [more ▼]

In market economies, homeownership is associated with positive ex- ternalities. Increasing the levels of homeownership has been an objective of governments for the last decades. The analysis of the determinants of tenure sta- tus provides information to this end. This paper proposes an econometric analysis of housing tenure in Belgium. We review the main variables that have been considered in the literature as influencing housing tenure, after what we estimate a logit model. We observe a strong influence of income and age on the probability of homeownership. Couple relationship and the presence of dependent children have a positive influence, but this influence is less significant. Urban location is associated with lower probability of homeownership, compared with other areas. Our observations follow the trends described for other countries in the literature. [less ▲]

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See detailUnifying and Extending User Story Models
Wautelet, Yves; Heng, Samedi ULiege; Kolp, Manuel et al

in Lecture Notes in Computer Science (2014, June), 8484

Within Agile methods, User Stories (US ) are mostly used as primary requirements artifacts and units of functionality of the project. The idea is to express requirements on a low abstraction basis using ... [more ▼]

Within Agile methods, User Stories (US ) are mostly used as primary requirements artifacts and units of functionality of the project. The idea is to express requirements on a low abstraction basis using natural language. Most of them are exclusively centered on the final user as only stakeholder. Over the years, some templates (in the form of concepts relating the WHO, WHAT and WHY dimensions into a phrase) have been proposed by agile methods practitioners or academics to guide requirements gathering. Using these templates can be problematic. Indeed, none of them define any semantic related to a particular syntax precisely or formally leading to various possible interpretations of the concepts. Consequently, these templates are used in an ad–hoc manner, each modeler having idiosyncratic preferences. This can nevertheless lead to an underuse of representation mechanisms, misunderstanding of a concept use and poor communication between stakeholders. This paper studies templates found in literature in order to reach unification in the concepts’ syntax, an agreement in their semantics as well as methodological elements increasing inherent scalability of US-based projects. [less ▲]

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See detailSpatial augmented reality in collaborative design training : articulation between I-space, We-space and Space-between
Ben Rajeb, Samia ULiege; Leclercq, Pierre ULiege

in Lecture Notes in Computer Science (2014), LNCS 8526 / vol 2(part 2), 343-353

This paper analyses the use of augmented reality in advanced project-based training in design. Our study considers how augmented environments can contribute to this type of group training : what types of ... [more ▼]

This paper analyses the use of augmented reality in advanced project-based training in design. Our study considers how augmented environments can contribute to this type of group training : what types of interaction spaces constitute these new learning environments and how are these spaces constructed so as to promote collective reflection ? [less ▲]

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See detailInteger Programs with Prescribed Number of Solutions and a Weighted Version of Doignon-Bell-Scarf’s Theorem
Aliev, Iskander; De Loera, Jesus; Louveaux, Quentin ULiege

in Lecture Notes in Computer Science (2014)

In this paper we study a generalization of the classical fesibility problem in integer linear programming, where an ILP needs to have a prescribed number of solutions to be considered solved. We first ... [more ▼]

In this paper we study a generalization of the classical fesibility problem in integer linear programming, where an ILP needs to have a prescribed number of solutions to be considered solved. We first provide a generalization of the famous Doignon-Bell-Scarf theorem: Given an integer k, we prove that there exists a constant c(k, n), depending only on the dimension n and k, such that if a polyhedron {x : Ax ≤ b} contains exactly k integer solutions, then there exists a subset of the rows of cardinality no more than c(k,n), defining a polyhedron that contains exactly the same k integer solutions. The second contribution of the article presents a structure theory that characterizes precisely the set Sg≥k (A) of all vectors b such that the problem Ax = b, x ≥ 0, x ∈ Zn , has at least k-solutions. We demonstrate that this set is finitely generated, a union of translated copies of a semigroup which can be computed explicitly via Hilbert bases computation. Similar results can be derived for those right-hand-side vectors that have exactly k solutions or fewer than k solutions. Finally we show that, when n, k are fixed natural numbers, one can compute in polynomial time an encoding of Sg≥k(A) as a generating function, using a short sum of rational functions. As a consequence, one can identify all right-hand-side vectors that have exactly k solutions (similarly for at least k or less than k solutions). Under the same assumptions we prove that the k-Frobenius number can be computed in polynomial time. [less ▲]

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