This position paper addresses online and open education. It presents a simple, yet comprehensive framework that can be adopted by any higher education institution in seek of: (1) clarification of terms and concepts related to online and open education, (2) awareness of issues and challenges to set up strategies for online or open learning, (3) informed choices and their impacts on operationalization actions, from an institutional point of view, (4) perspectives on crucial issues, such as mobility, that HEI faces in a context of internationalization, (5) awareness of policymakers and teachers on what open and online education is.

Motivated by conversations with operators and by possibilities to unlock future Internet-based applications, we study how to enable Internet Service Providers (ISPs) to reliably offer connectivity through disjoint paths as an advanced, value-added service. As ISPs are increasingly deploying Segment Routing (SR), we focus on implementing such service with SR. We introduce the concept of robustly disjoint paths, pairs of paths that are constructed to remain disjoint even after an input set of failures, with no external intervention (e.g., configuration change). We extend the routing theory, study the problem complexity, and design efficient algorithms to automatically compute SR-based robustly disjoint paths. Our algorithms enable a fully automated approach to offer the disjoint-path connectivity, based on configuration synthesis. Our evaluation on real topologies shows that such an approach is practical, and scales to large ISP networks.

Reifying a constraint c consists in associating a Boolean variable b with c such that c is satisfied if and only if b is true, which can be denoted by c^{reif}: cb. Reification is useful for logically combining constraints and counting how many reified constraints can be satisfied. Since table constraints play an important role within constraint programming, in this paper, we are interested in their reification. We introduce a filtering algorithm that allows us to establish generalized arc consistency on reified table constraints, with no spatial overhead. We also propose a flexible approach that can generally reify any subsets of constraints. We show the practical interest of our work on the Max-CSP problem and a variation of the subgraph isomorphism problem.

The smart table constraint represents a powerful modeling tool that has been recently introduced. This constraint allows the user to represent compactly a number of well-known (global) constraints and more generally any arbitrarily structured constraints, especially when disjunction is at stake. In many problems, some constraints are given under the basic and simple form of tables explicitly listing the allowed combinations of values. In this paper, we propose an algorithm to convert automatically any (ordinary) table into a compact smart table. Its theoretical time complexity is shown to be quadratic in the size of the input table. Experimental results demonstrate its compression efficiency on many constraint cases while showing its reasonable execution time. It is then shown that using filtering algorithms on the resulting smart table is more efficient than using state of the art filtering algorithms on the initial table.

To guarantee correct operation of their networks, operators have to promptly detect and diagnose data-plane issues, like broken interface cards or link failures. Networks are becoming more complex, with a growing number of Equal Cost MultiPath (ECMP) and link bundles. Hence, some data-plane problems (e.g. silent packet dropping at one router) can hardly be detected with control-plane protocols or simple monitoring tools like ping or traceroute. In this paper, we propose a new technique, called SCMon, that enables continuous monitoring of the data-plane, in order to track the health of all routers and links. SCMon leverages the recently proposed Segment Routing (SR) architecture to monitor the entire network with a single box (and no additional monitoring protocol). In particular, SCMon uses SR to (i) force monitoring probes to travel over cycles; and (ii) test parallel links and bundles at a per-link granularity. We present original algorithms to compute cycles that cover all network links with a limited number of SR segments. Further, we prototype and evaluate SCMon both with simulations and Linux-based emulations. Our experiments show that SCMon quickly detects and precisely pinpoints data-plane problems, with a limited overhead.

Ultra-low latency is a key component of safety-critical operations such as robot-assisted remote surgery or financial applications where every single millisecond counts. In this paper, we show how network operators can build upon the recently proposed Segment Routing architecture to provide a traffic duplication service to better serve the users of such demanding applications. We propose the first implementation of Segment Routing in the Linux kernel and leverage it to provide a traffic duplication service that sends packets over disjoint paths. Our experiments show that with such a service existing TCP stacks can preserve latency in the presence of packet losses. We also propose and evaluate an efficient algorithm that computes disjoint paths that can be realised by using segments. Our evaluation with real and synthetic network topologies shows that our proposed algorithms perform well in large networks.

This paper presents a novel approach for automated test data generation of imperative programs containing integer, boolean and/or float variables. It extends our previous work to programs with procedure calls and arrays. A test program (with procedure calls) is represented by an Interprocedural Control Flow Graph (ICFG). The classical testing criteria (statement, branch, and path coverage), widely used in unit testing, are extended to the ICFG. For path coverage, the specified path is transformed into a path constraint. Our previous consistency techniques, the core idea behind the solving of path constraints, have been extended to handle procedural calls and operations with arrays. For statement (and branch) coverage, paths reaching the specified node or branch are dynamically constructed. The search for suitable paths is guided by the interprocedural control dependences of the program. The search is also pruned by a new specialized consistency filter. Finally, test data are generated by the application of the proposed path coverage algorithm. A prototype has been implemented. Experiments show the feasibility of the approach.

Biochemical pathways such as metabolic, regulatory or signal transduction pathways can be viewed as interconnected processes forming an intricate network of functional and physical interactions between molecular species in the cell. The amount of information available on such pathways for different organisms is increasing very rapidly. This is offering the possibility of performing various analyses on the structure of the full network of pathways for one organism as well as across different organisms, and has therefore generated interest in developing databases for storing and managing this information. Analysing these networks remains far from straightforward owing to the nature of the databases, which are often heterogeneous, incomplete or inconsistent. Pathway analysis is hence a challenging problem in systems biology and in bioinformatics. Various forms of data models have been devised for the analysis of biochemical pathways. This paper presents an overview of the types of models used for this purpose, concentrating on those concerned with the structural aspects of biochemical networks. In particular, the different types of data models found in the literature are classified using a unified framework. In addition, how these models have been used in the analysis of biochemical networks is described. This enables us to underline the strengths and weaknesses of the different approaches, as well as to highlight relevant future research directions.

The paper presents a novel approach for automated test data generation of imperative programs containing integer, boolean and/or float variables. Our approach is based on consistency techniques integrating integer and float variables. We handle statement, branch and path coverage criteria. Our purpose is thus to automatically generate test data that will cause the program to execute a statement, to traverse a branch or to traverse a specified path. For path coverage, the specified path is transformed into a path constraint which is solved by an interval-based constraint solving algorithm handling integer, boolean and real variables. A valid test input is then extracted from the interval solutions. For statement (and branch) coverage, a path reaching the specified statement or branch is dynamically constructed. Our algorithm for path coverage is then applied. The search for a suitable path and the solving of path constraints make extensive use of consistency techniques. We propose a simple consistency notion called eBox consistency, for generalizing box consistency to integer and float variables. The eBox consistency is sufficient for our purpose. A prototype has been developed and experimental results show the feasibility of our approach. This work is an extension of work by A. Gotlieb (2000) for float and boolean variables.