1,721,161 research outputs found
Dealing with Inconsistency and Incompleteness in Data Integration
Full text linkMarco Schaerf, Giuseppe Di Battista, Domenico SaccÃ
Proceedings of the Twenty-Seventh ACM SIGMOD-SIGACT-SIGART Symposium on Principles of Database Systems
No full textPODS 2008, JUNE 9-11, 2008, VANCOUVER, BC, CANADA ACM 200
Ontology-based Document Spanning Systems for Information Extraction
Full text linkInformation Extraction (IE) is the task of automatically organizing in a structured form data extracted from free text documents. In several contexts, it is often desirable that extracted data are then organized according to an ontology, which provides a formal and conceptual representation of the domain of interest. Ontologies allow for a better data interpretation, as well as for their semantic integration with other information, as in Ontology-based Data Access (OBDA), a popular declarative framework for data management where an ontology is connected to a data layer through mappings. However, the data layer considered so far in OBDA has consisted essentially of relational databases, and how to declaratively couple an ontology with unstructured data sources is still unexplored.
By leveraging the recent study on document spanners for rule-based IE by Fagin et al., in this paper we propose a new framework that allows to map text documents to ontologies, in the spirit of OBDA. We investigate the problem of answering conjunctive queries in this framework. For ontologies specified in the Description Logics DL-LiteR and DL-LiteF , we show that the problem is polynomial in the size of the underlying documents. We also provide algorithms to solve query answering by rewriting the input query on the basis of the ontology and its mapping towards the source documents. Through these techniques we pursue a virtual approach, similar to that typically adopted in OBDA, which allows us to answer a query without having to first populate the entire ontology. Interestingly, for DL-LiteR both the spanners used in the mapping and the one computed by the rewriting algorithm belong to the same class of expressiveness. This holds also for DL-LiteF , modulo some limitations on the form of the mapping. These results say that in these cases our framework can be easily implemented by decoupling ontology management and document access, which can be delegated to an external IE system able to compute the extraction rules we use in the mapping
Web Reasoning and Rule Systems: 7th International Conference, RR 2013, Mannheim, Germany, July 27-29, 2013, Proceedings
No full textThis book constitutes the refereed proceedings of the 7th International Conference on Web Reasoning and Rule Systems, RR 2013, held in Manheim, Germany in July 2013. The 19 revised research papers and 4 technical communications presented together with 2 invited talks and 1 tutorial talk were carefully reviewed and selected from 34 submissions. The scope of conference is decision making, planning, and intelligent agents, reasoning, machine learning, knowledge extraction and IR technologies, large-scale data management and reasoning on the web of data, data integration, dataspaces and ontology-based data access, non-standard reasoning, algorithms for distributed, parallelized, and scalable reasoning, and system descriptions and experimentation
BPM4ED: A research project for designing 21st-century schools
No full textSchools and teaching are quickly changing due to the continuous evolution of the world and society, and thus new forms of education are required: on the one side, the emergence of smart cities and smart communities demands for active citizens interacting with institutions, and on the other side ICT is modifying both the learning environments and the training models. The so-called "21st century schools" differ from the current ones in almost all the aspects: building architecture, furniture, teaching and learning methods. This new kind of school is spreading all over the world, and governments recognizing the importance of an efficient, modern and up-to-date education system are committed in the design and implementation of these new schools. But some problems make this scenario confusing, preventing an ordered development of this new kind of schools: first, the lack of theoretical models able to represent the "21st century school" features; second, tools to manage and design these schools and their services and activities are, when they exist, based on the old paradigms (i.e., the traditional school with classrooms, etc.) and are not still integrated in an unique toolbox able to support the whole school operations and management. In this paper, the ongoing BPM4ED (Business Process Management for EDucation) research project is described: schools are seen as organizations and business process management techniques are used to analyze and classify them; the final and ambitious goals of the project are the development of a design methodology for "21st century schools" and the definition, design and implementation of a new class of integrated tools, possibly including the existing ones, to manage all the school activities and services
Data integration with preferences among sources
No full textData integration systems represent today a key technological infrastructure for managing the enormous amount of information even more and more distributed over many data sources, often stored in different heterogeneous formats. Several different approaches providing transparent access to the data by means of suitable query answering strategies have been proposed in the literature. These approaches often assume that all the sources have the same level of reliability and that there is no need for preferring values "extracted" from a given source. This is mainly due to the difficulties of properly translating and reformulating source preferences in terms of properties expressed over the global view supplied by the data integration system. Nonetheless preferences are very important auxiliary information that can be profitably exploited for refining the way in which integration is carried out. In this paper we tackle the above difficulties and we propose a formal framework for both specifying and reasoning with preferences among the sources. The semantics of the system is restated in terms of preferred answers to user queries, and the computational complexity of identifying these answers is investigated as well
Towards efficient and practical solutions for ontology-based data management
No full textThis paper presents the research summary of my Ph.D. plan, which is currently in the early stages of its development. The objectives around which my work is focusing and that I will continue to pursue throughout the remainder of my doctoral activities are the development of tools and the definition of a methodology for the execution of those tasks that are typically performed when working with ontologies in the context of Ontology-Based Data Access (OBDA). The objective of this methodology is to guide the ontology engineer through ontology design, representation and approximation, and the issues I will address in order to provide the necessary tools to achieve this goal are the optimization of ontology classification in DL-Lite, the definition of a graphical language tailored towards ontologies, and the study of approximation of ontologies in expressive languages into DL-Lite logics. Such methodology proves to be necessary when facing the numerous challenges that often arise in real-world scenarios, in which the amount of data that is managed by information systems, and the processes that manage and act on this data grow continuously. © 2013 ACM
- …
