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## Seminari proposti nell'Anno Accademico 2009/2010

• ### Minimizing total weighted earliness-tardiness on a single machine around a small common due date: an FPTAS using quadratic knapsack

• Docente: Hans Kellerer
• Data: Lunedì 20 Dicembre 2010, ore 14:30
• Aula: Sala Riunioni DIA, 1° piano
• Abstract: We design a fully polynomial-time approximation scheme (FPTAS) for a single machine scheduling problem to minimize the total weighted earliness and tardiness with respect to a common restrictive due date. Notice for this problem no constant-ratio approximation algorithm has been known so far. Our approach is based on adopting an FPTAS for a special version of the knapsack problem to minimize a convex quadratic non-separable function. For the continuous relaxation of such a knapsack problem we give an algorithm of a quadratic time complexity. The running time of each presented FPTAS is strongly polynomial.
Per ulteriori informazioni rivolgersi a G. Nicosia (nicosia@dia.uniroma3.it, tel. 06 57333455).
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• ### On the Queue Number of Planar Graphs

• Docente: Fabrizio Frati
• Data: Giovedì 21 Ottobre 2010, ore 17.30
• Aula: Sala Riunioni DIA, 1° piano
• Abstract: We prove that planar graphs have $O(\log^4 n)$ queue number, thus improving upon the previous $O(\sqrt n)$ upper bound. Consequently, planar graphs admit 3D straight-line crossing-free grid drawings in $O(n \log^c n)$ volume, for some constant $c$, thus improving upon the previous $O(n^{3/2})$ upper bound.
This is a joint work with Giuseppe Di Battista (Roma Tre University) and Janos Pach (EPFL Lausanne and Renyi Institute Budapest)
The same presentation will be given at FOCS 2010, 50th Annual IEEE Symposium on Foundations of Computer Science, Las Vegas, October 23-26, 2010
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• ### Assigning AS Relationships to Satisfy the Gao-Rexford Conditions

• Docente: Massimo Rimondini (DIA)
• Data: Giovedì 16 Settembre 2010, ore 12.00
• Aula: Sala Riunioni DIA, 1° piano
• Abstract: Compliance with the Gao-Rexford conditions is perhaps the most realistic explanation of Internet routing stability, although BGP is renowned to be prone to oscillations. Informally, the Gao-Rexford conditions assume that (i) the business relationships between Internet Service Providers (ISPs) yield a hierarchy, (ii) each ISP behaves in a rational way, i.e., it does not offer transit to other ISPs for free, and (iii) each ISP ranks routes through customers better than routes through providers and peers. We show an efficient algorithm that, given a BGP configuration, checks whether there exists an assignment of peer-peer and customer-provider relationships that complies with the Gao-Rexford conditions. Also, we show that preferring routes through peers to those through providers, although more suitable than the original formulation of Condition (iii) to describe the business relationships between ISPs, makes the problem NP-hard. The above results hold both in the well known theoretical framework used to model BGP and in a more realistic setting where (i) local preferences are assigned on a per-neighbor basis and (ii) transit is allowed from/to specific neighbor pairs. Observe that the latter setting, where policy complexity only depends on the number of neighbors, is very close to the way in which operators typically configure routers.
This is a joint work with Luca Cittadini (Roma Tre University), Giuseppe Di Battista (Roma Tre University), Thomas Erlebach (University of Leicester), and Maurizio Patrignani (Roma Tre University)
The same presentation will be given at the 18th IEEE International Conference on Network Protocols, Kyoto, Japan, Oct. 5 - 8, 2010
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• ### Top-k Approximate Subtree Matching

• Docente: Denilson Barbosa (University of Alberta, Edmonton)
• Data: Lunedì 5 Luglio 2010, ore 15.00
• Aula: N7 DIA
• Abstract: We consider the top-k Approximate Subtree Matching (TASM) problem: finding the k best matches of a small query tree, e.g., a DBLP article with 15 nodes, in a large document tree, e.g., DBLP with 26M nodes, using the canonical tree edit distance as a similarity measure between subtrees. Evaluating the tree edit distance for large XML trees is difficult: the best known algorithms have cubic runtime and quadratic space complexity, and, thus, do not scale. Our solution is TASM-postorder, a memory-efficient and scalable TASM algorithm. We prove an upper-bound for the maximum subtree size for which the tree edit distance needs to be evaluated. The upper bound depends on the query and is independent of the document size and structure. A core problem is to efficiently prune subtrees that are above this size threshold. We develop an algorithm based on the prefix ring buffer that allows us to prune all subtrees above the threshold in a single postorder scan of the document. The size of the prefix ring buffer is linear in the threshold. As a result, the space complexity of TASM-postorder depends only on k and the query size, and the runtime of TASM-postorder is linear in the size of the document. Our experimental evaluation on large synthetic and real XML documents confirms our analytic results.
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• ### A Framework for Automatic Schema Mapping Verification Through Reasoning

• Docente: Denilson Barbosa (University of Alberta, Edmonton)
• Data: Giovedì 1 Luglio 2010, ore 15.00
• Aula: N7 DIA
• Abstract: We advocate an automated approach for verifying mappings between source and target databases in which semantics are taken into account, and that avoids two serious limitations of current verification approaches: reliance on availability of sample source and target instances, and reliance on strong statistical assumptions. We discuss how our approach can be integrated into the workflow of state-of-the-art mapping design systems, and all its necessary inputs. Our approach relies on checking the entailment of verification statements derived directly from the schema mappings and from semantic annotations to the variables used in such mappings. We discuss how such verification statements can be produced and how such annotations can be extracted from different kinds of alignments of schemas into domain ontologies. Such alignments can be derived semi-automatically; thus, our framework might prove useful in also greatly reducing the amount of input from domain experts in the development of mappings.
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• ### An Environment for Building, Exploring and Querying Social Networks

• Docente: Denilson Barbosa (University of Alberta, Edmonton)
• Data: Mercoledì 30 Giugno 2010, ore 15.00
• Aula: N3 DIA
• Abstract: Social network analysis aims at uncovering and understanding the structures and patterns resulting from social inter- actions among individuals and organizations engaged in a common activity. Since the early days of the field, networks are modeled as graphs modeling social actors and the relations between them. The field has become very active with the maturity of computational machinery to handle large-scale graphs, and, more recently, the automated gathering of social data. This talk will describe ReaSoN: an ongoing work towards building a system for extracting, visualizing and exploring social networks. The talk will focus on the underlying infrastructure behind ReaSoN, the extraction of social networks from structured citation databases as well as unstructured social media, some data management issues that arise in building such systems, notions of network visibility and the processing of user-defined queries. As an illustration, the talk covers the first incarnation of ReaSoN: a social network resulting from academic research built from ACM DL, DBLP and Google Scholar data. In doing so, ReaSoN contributes to the understanding as well as fostering of the social networks underlying research.
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• ### Query Optimization in the Deep Web

• Docente: Andrea Cali' (Brunel University), Davide Martinenghi (Politecnico di Milano)
• Data: Giovedi' 10 Giugno 2010, ore 11:30
• Aula: N7 DIA
• Abstract: The term Deep Web refers to the data content that is created dynamically as the result of a specific search on the Web. In this respect, such content resides outside web pages, and is only accessible through interaction with the web site – typically via HTML forms. It is believed that the size of the Deep Web is several orders of magnitude larger than that of the so-called Surface Web, i.e., the web that is accessible and indexable by search engines. Usually, data sources accessible through web forms are modeled by relations that require certain fields to be selected – i.e., some fields in the form need to be filled in. These requirements are commonly referred to as access limitations in that access to data can only take place according to given patterns. Besides data accessible through web forms, access limitations may also occur i) in legacy systems where data scattered over several files are wrapped as relational tables, and ii) in the context of Web services, where similar restrictions arise from the distinction between input parameters and output parameters. In such contexts, computing the answer to a user query cannot be done as in a traditional database; instead, a query plan is needed that provides the best answer possible while complying with the access limitations. In these talks, we illustrate the semantics of answers to queries over data sources under access limitations and present techniques for query answering in this context. We show different techniques to optimize query answering both at the time of the query plan generation and at the time of the execution of the query plan. We analyze the influence of integrity constraints on the sources, of the kind that is usually found in database schemata, on query answering. We present prototype systems that are aimed at querying the deep web, and show their achievements.
• Materiale: pdf (~4.93 MB)
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• ### Semantic based Discovery and Management of Content, Services and Software

• Docente: Beniamino Di Martino (Seconda Universita' di Napoli)
• Data: Martedì 23 Marzo 2010, ore 14.30
• Aula: Sala Riunioni DIA
• Abstract: -
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• ### Geometric and Topological Features of Euclidean Minimum Spanning Trees

• Docente: Professor Michael Kaufmann (University of Tubingen)
• Data: Giovedì 18 Marzo 2010, ore 15.00
• Aula: Sala Riunioni DIA
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## Seminari proposti nell'Anno Accademico 2008/2009

• ### Leveraging Data and Structure in Ontology Integration

• Docente: Professoressa Renee Miller (University of Toronto)
• Data: Lunedì 9 Novembre 2009, ore 14.30
• Aula: N1 piano terra DIA
• Abstract: There is a great deal of research on schema and ontology integration which makes use of rich logical constraints to reason about the structural and logical alignment of schema and ontologies. There is also considerable work on matching data instances from heterogeneous schema or ontologies. However, little work exploits the fact that ontologies include both data and structure. We provide a first step in closing this gap with a new algorithm (Iliads) that integrates both data matching and logical reasoning to achieve better matching of ontologies. We evaluate our algorithm on a set of pairs of OWL Lite ontologies with the schema and data matchings found by human reviewers. We compare against two systems - the ontology matching tool FCA-merge and the schema matching tool COMA++. This is preliminary work in this area and the talk will highlight further opportunities for integrating data matching (including entity resolution) with schema matching and mapping. This is joint work with Octavian Udrea and Lise Getoor of the University of Maryland which appeared in SIGMOD 2007.
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• ### Roma Spring Framework Meeting

• Docente: -
• Data: Sabato 31 Ottobre 2009, ore 8.30
• Aula: Aule N10 - N11 DIA
• Abstract: -
• Materiale: -
• Pagina Web: Programma

• ### Learning-from-Observation: from assembly plan through dancing humanoid

• Docente: Prof. Katsushi Ikeuchi (University of Tokyo)
• Data: Giovedì 8 Ottobre 2009, ore 15.00
• Aula: Sala Riunioni DIA
• Abstract:We have been developing the paradigm referred to as programming-by-demonstration.The method involves simple observation of what a human is doing and generation of robot programs to mimic the same operations. The first half of this talk presents the history of what we have done so far under this paradigm. Here, we emphasize the top-down approach to utilize pre-defined, mathematically derived, task-and-skill models for observing and mimicking human operations. We will show several examples of task-and-skill models applicable in different domains. Then, the second half focuses on our newest effort to make a humanoid robot dance Japanese folk dances using the same paradigm. Human dance motions are recorded using optical or magnetic motion-capture systems. These captured motions are segmented into tasks using motion analysis, music information, and task-and-skill models. We can characterize personal differences of dance using task-and-skill models. Then, we can map these motion models onto robot motions by considering dynamic and structural differences between human and robot bodies. As a demonstration of our system, I will show a video in which a humanoid robot performs a Japanese folk dance.
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• ### Extending Convex Drawings of Graphs

• Docente: Prof.ssa Seok-Hee Hong (University of Sydney)
• Data: Giovedì 1 Ottobre 2009, ore 16.00
• Aula: Sala Riunioni DIA
• Abstract:Graph Drawing has attracted much attention over the last twenty years due to its wide range of applications such as VLSI design, social networks, software engineering and bioinformatics. A straight-line drawing is called a "convex drawing" if every facial cycle is drawn as a convex polygon. Convex representation of graphs is a well-established aesthetic in Graph Drawing, however not all planar graphs admit a convex drawing as observed by Steinitz, Tutte and Thomassen earlier. In this talk, we introduce two new notions of drawings, "inner-convex drawings" and "star-shaped drawings" , as natural extensions of convex drawings. We present various results including characterisation, testing, embedding and drawing algorithms. Our results extend the classical results by Tutte, and include results by Thomassen and Steinitz as a special case.
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• ### Information Discovery on Vertical Domains

• Docente: Vagelis Hristidis (Florida International University)
• Data: Martedì 14 Marzo 2009, ore 11.30
• Aula: Sala riunioni DIA
• Abstract: As the amount of available data increases, the problem of information discovery, often referred to as finding the needle in the haystack problem, becomes more pressing. The most successful search applications today are the general purpose Web search engines and the well-structured database querying (e.g., SQL). Directly applying these two search models to specific domains is ineffective since they ignore the domain semantics e.g., meaning of object associations e.g., a biologist wants to see different results from a physician for the same query on PubMed. We present challenges and techniques to achieve effective information discovery on vertical domains by modeling the domain semantics and its users, and exploiting the knowledge of domain experts. Our focal domains are products marketplace, biological data, clinical data, and bibliographic data. This project is being funded by NSF
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• ### Ecology of Robots

• Docente: Chair: Federica Pascucci (DIA). Speakers: Alessandro Saffiotti (Universita' di Orebro, Svezia), Maurizio Di Rocco (DIA), Attilio Priolo (DIA), Andrea Gasparri (DIA), Paolo Stegagno (La Sapienza), Fabrizio Flacco (La Sapienza), Marilena Vendittelli (La Sapienza)
• Data: 6 maggio 2009, ore 9.30
• Aula: Aula N3, DIA
• Pagina Web: Pagina Web

• ### Model Enhancement in Data Mining: Calibration, ROC Analysis, Model Combination and domain users bMimetic Models

• Docente: José Hernández-Orallo (Universidad Politécnica de Valencia)
• Data: Lunedì 18 maggio 2009, ore 11.30
• Aula: Sala riunioni DIA
• Abstract: Outline: Motivation. Data Mining Models. Model Calibration. Context (ROC) Analysis. Model Combination. Model Simplification, Mimetic Models. General idea. Specific implementations for calibration, adaptation, combination, simplification and revision. Conclusions.
• Materiale: Materiale
• Pagina Web: Pagina Web

• ### Biomechanics & allied disciplines: a casual bird's-eye view

• Docente:
• Roberto Contro (LaBS-Laboratory of Biological Structural Mechanics, Politecnico di Torino)
• Marcelo Epstein (Faculty of Mechanical and Manufacturing Engineering & Adjunct Professor, Faculty of Kinesiology and Humanities, University of Calgary)
• Antonio Di Carlo (LaMS-Modelling & Simulation Lab, Università Roma Tre)
• Data: Giovedì 19 febbraio, ore 10
• Aula: Aula Seminari (Terzo piano) Dipartimento di Strutture - via Corrado Segre 6
• Abstract: -
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Ultimo aggiornamento: 17/12/2010