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Petri nets are a powerful formalism for the specification and verification of concurrent systems such as sequential and manufacturing systems. To take into account efficiently the time parameter different extensions have been developed in the literature, each one being dependent on the application considered. In this paper, a new control technique for p-time Petri nets is proposed. It is based on the firing instant notion and it consists in determining a system of inequalities generated for a possible evolution (in terms of a feasible firing sequence for the untimed underlying Petri net) of the model considered. This system can be used to check reachability problems as well as evaluating the performances of the model considered and determining the associated control for a definite functioning mode. Furthermore, the proposed approach is not restricted to subclasses or safe Petri nets. © 2010 Lavoisier, Paris.

Bonhomme P.,Portalis
International Journal of Advanced Manufacturing Technology | Year: 2011

The increasing complexity of manufacturing systems gives rise to the development of new formal methods allowing to handle their particularities. Petri nets are a powerful formalism for the specification and verification of concurrent systems including sequential systems and manufacturing systems. To deal with systems whose time issues become fundamental, different time Petri nets extensions have been developed in the literature, each one being dependent on the application considered. For the time critical systems, their correctness depends not only on the logic correctness but also on the time constraints. Timing issues are essential. In this paper, a new method of analysis and control for P-time Petri nets is proposed. It is based on the firing instant notion and exploits a constraint graph approach. © 2011 Springer-Verlag London Limited.

Bonhomme P.,Portalis
19th IEEE International Conference on Emerging Technologies and Factory Automation, ETFA 2014 | Year: 2014

This paper focuses on the problem of estimating the marking of a P-time labeled Petri net with partial information. The set of transitions is partitioned into those labeled with the empty string e called silent, as their firing cannot be detected, and the observable ones. The proposed approach is based on the observation of transitions labels thanks to the synthesis of a state observer obtained from the behavior of the untimed underlying Petri net. A procedure that, given an observed word (sequence of labels defined over a given alphabet) with their occurrence dates, allows to determine the set of states consistent with the considered observation is provided, under the assumption of non-Zenoness of the subnet induced by the set of unobservable transitions. Furthermore, a source of nondeterminism is added as the case of indistinguishable transitions (transitions sharing the same label) is also considered. The method relies on the schedulability analysis of particular firing sequences, namely the candidates firing sequences and does not require the building of the state classes graph although the time is modeled as intervals. © 2014 IEEE.

Stamatopoulos N.,Institute of Informatics and Telecommunications National Center for Scientific Research Demokritos | Gatos B.,Institute of Informatics and Telecommunications National Center for Scientific Research Demokritos | Louloudis G.,Institute of Informatics and Telecommunications National Center for Scientific Research Demokritos | Pal U.,Indian Statistical Institute | Alaei A.,Portalis
Proceedings of the International Conference on Document Analysis and Recognition, ICDAR | Year: 2013

This paper presents the results of the Handwriting Segmentation Contest that was organized in the context of the ICDAR2013. The general objective of the contest was to use well established evaluation practices and procedures to record recent advances in off-line handwriting segmentation. Two benchmarking datasets, one for text line and one for word segmentation, were created in order to test and compare all submitted algorithms as well as some state-of-the-art methods for handwritten document image segmentation in realistic circumstances. Handwritten document images were produced by many writers in two Latin based languages (English and Greek) and in one Indian language (Bangla, the second most popular language in India). These images were manually annotated in order to produce the ground truth which corresponds to the correct text line and word segmentation results. The datasets of previously organized contests (ICDAR2007, ICDAR2009 and ICFHR2010 Handwriting Segmentation Contests) along with a dataset of Bangla document images were used as training dataset. Eleven methods are submitted in this competition. A brief description of the submitted algorithms, the evaluation criteria and the segmentation results obtained from the submitted methods are also provided in this manuscript. © 2013 IEEE.

Pham T.A.,Portalis | Delalandre M.,Portalis | Barrat S.,Portalis
Proceedings of the International Conference on Document Analysis and Recognition, ICDAR | Year: 2011

This paper presents a new approach for logo detection exploiting contour based features. At first stage, pre-processing, contour detection and line segmentation are done. These processes result in set of Outer Contour Strings (OCSs) describing each graphics and text parts of the documents. Then, the logo detection problem is defined as a region scoring problem. Two types of features, coarse and finer ones, are computed from each OCS. Coarse features catch graphical and domain information about OCSs, such as logo positions and aspect ratios. Finer features characterize the contour regions using a gradient based representation. Using these features, we employ regression fitting to score how likely an OCS takes part of a logo region. A final step of correction helps with the wrong segmentation cases. We present experiments done on the Tobacco-800 dataset, and compare our results with the literature. We obtain interesting results compared to the best systems. © 2011 IEEE.

Bourquin P.,Portalis | Ramel J.-Y.,Portalis
CORIA 2014 - Conference en Recherche d'Infomations et Applications - 11th French Information Retrieval Conference. CIFED 2014 - Colloque International Francophone sur l'Ecrit et le Document | Year: 2014

This paper describes a new framework dedicated to layout analysis and content extraction in digitized documents. This new method is based on an original sub-tree transformation and matching algorithm that includes a constraint verification step. The subtree structures represent the elements of content to be extracted as well as the current state of the interpretation process. The sub-tree transformation and matching algorithm can be used incrementally in order to build adaptive processing chains making the tree corresponding to the whole document evolving. The originality of the proposed framework comes from the possibility provided to the users to generate interactively, and as they wants, many different image analysis scenarios by just applying sequentially some specific transformations on a tree structure that represents the layout of the document images.

Tuong N.H.,Portalis | Soukhal A.,Portalis | Billaut J.-C.,Portalis
Journal of Scheduling | Year: 2012

In this paper, we consider the problem of scheduling independent jobs when several agents compete to perform their jobs on a common single processing machine. Each agent wants to minimise its cost function, which depends exclusively on its jobs and we assume that a global cost function concerning the whole set of jobs has to be minimised. This cost function may correspond to the global performance of the workshop or to the global objective of the company, independent of the objectives of the agents. Classical regular objective functions are considered and both the e-constraint and a linear combination of criteria are used for finding compromise solutions. This new multi-agent scheduling problem is introduced into the literature and simple reductions with multicriteria scheduling and multi-agent scheduling problems are established. In addition, the complexity results of several problems are proposed and a dynamic programming algorithm is given. © Springer Science+Business Media, LLC 2011.

Sadi F.,Portalis | Soukhal A.,Portalis | Billaut J.-C.,Portalis
RAIRO - Operations Research | Year: 2014

In this study, we consider a scheduling environment with m(m ≥ 1) parallel machines. The set of jobs to schedule is divided into K disjoint subsets. Each subset of jobs is associated with one agent. The K agents compete to perform their jobs on common resources. The objective is to find a schedule that minimizes a global objective function f 0, while maintaining the regular objective function of each agent, f k, at a level no greater than a fixed value, εk(fk ε {fkmax,∑fk}, k=0, K f k ε {f max k, ∑ f k}, k = 0,K). This problem is a multi-agent scheduling problem with a global objective functio. In this study, we consider the case with preemption and the case without preemption. If preemption is allowed, we propose a polynomial time algorithm based on a network flow approach for the unrelated parallel machine case. If preemption is not allowed, we propose some general complexity results and develop dynamic programming algorithms.

Bonhomme P.,Portalis
IEEE International Conference on Automation Science and Engineering | Year: 2011

This paper addresses the schedulability analysis of real-time systems modeled by P-Time Petri nets. The proposed approach is based on the consideration of the reachability graph of the (untimed) underlying Petri net of the studied model. The schedulability analysis is then conducted in two steps. Once a feasible firing sequence (called occurrence sequence) is highlighted, thanks to a firing instant based approach the timing constraints are added, yielding an inequality system representing its timing behavior. Thus, deciding whether a firing sequence is schedulable or not takes the form of the solution of a linear programming problem. Furthermore, the modification of a timing constraint does not alter the form of the obtained system, helping adjusting accurately timing properties in a specifications refinement purpose. © 2011 IEEE.

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