Consistent Query Answering without Repairs in Tables with Nulls and Functional Dependencies

In this paper, we study consistent query answering in tables with nulls and functional dependencies. Given such a table T, we consider the set Tuples of all tuples that can be built up from constants appearing in T, and we use set theoretic semantics for tuples and functional dependencies to characterize the tuples of Tuples in two orthogonal ways: first as true or false tuples, and then as consistent or inconsistent tuples. Queries are issued against T and evaluated in Tuples. In this setting, we consider a query Q: select X from T where Condition over T and define its consistent answer to be the set of tuples x in Tuples such that: x is a true and consistent tuple with schema X and there exists a true super-tuple t of x in Tuples satisfying the condition. We show that, depending on the status that the super-tuple t has in Tuples, there are different types of consistent answer to Q. The main contributions of the paper are: (a) a novel approach to consistent query answering not using table repairs; (b) polynomial algorithms for computing the sets of true-false tuples and the sets of consistent-inconsistent tuples of Tuples; (c) polynomial algorithms in the size of T for computing different types of consistent answer for both conjunctive and disjunctive queries; and (d) a detailed discussion of the differences between our approach and the approaches using table repairs.Comment: 42 page

A Functional Model for Data Analysis and Result Visualization

In several Web based applications (e-commerce, e- learning, digital libraries, etc.) one needs to display a dense array of information in a small amount of space (such as a screen) in a manner that communicates clearly and immediately. The information displayed is usually aggregates of results obtained through analysis of large amounts of data. We present a functional model that supports the data analysis and aggregation process, and a prototype that supports casual users in doing the following: (a) construct an analytic query visually, in an interactive manner, (b) visualize the aggregate result in a user selected mode (histogram, pie, etc.), (c) explore the query result by providing equivalent representations at different aggregation levels or for different parameter values selected by the user

Characteristics of Citizen-contributed Geographic Information

Ponencias, comunicaciones y pósters presentados en el 17th AGILE Conference on Geographic Information Science "Connecting a Digital Europe through Location and Place", celebrado en la Universitat Jaume I del 3 al 6 de junio de 2014.Current Internet applications have been increasingly incorporating citizen-contributed geographic information (CCGI) with much heterogeneous characteristics. Nevertheless, despite their differences, several terms are often being used interchangeably to define CCGI types, in the existing literature. As a result, the notion of CCGI has to be carefully specified, in order to avoid vagueness, and to facilitate the choice of a suitable CCGI dataset to be used for a given application. To address the terminological ambiguity in the description of CCGI types, we propose a typology of GI and a theoretical framework for the evaluation of GI in terms of data quality, number and type of contributors and cost of data collection per observation. We distinguish between CCGI explicitly collected for scientific or socially-oriented purposes. We review 27 of the main Internet-based CCGI platforms and we analyse their characteristics in terms of purpose of the data collection, use of quality assurance and quality control (QA/QC) mechanisms, thematic category, and geographic extents of the collected data. Based on the proposed typology and the analysis of the platforms, we conclude that CCGI differs in terms of data quality, number of contributors, data collection cost and the application of QA/QC mechanisms, depending on the purpose of the data collection

Museum Collections and the Semantic Web

The paper discusses some current trends in the area of development and use of semantic portals for accessing heterogeneous museum collections on the Semantic Web. The presentation is focused on some issues concerning metadata standards for museums, museum collections ontologies and semantic search engines. A number of design considerations and recommendations are formulated.The Fourth International Conference on Digital Presentation and Preservation of Cultural and Scientific Heritage—DiPP2014 is supported by the Ministry of Education and Science and is under the patronage of UNESCO

Query Enrichment for Image Collections by Reuse of Classification Rules

User queries over image collections, based on semantic similarity, can be processed in several ways. In this paper, we propose to reuse the rules produced by rule-based classifiers in their recognition models as query pattern definitions for searching image collections

Deciphering the atmospheric properties of hot gas giant exoplanets via ground-based transmission spectroscopy

Transiting hot gas giant exoplanets are great targets for atmospheric investigations due to their extended atmospheres and their strong obscuring effect on the observed starlight when they pass in front of their host star. Transmission spectroscopy can probe transiting exoplanets at various wavelengths and, hence, reveal the dominant opacity sources in specific regions of their atmospheres. In this thesis, I present groundbased transmission spectroscopy obtained in the optical for three exoplanets and describe the various analysis methods explored in order to produce the characteristic transmission spectrum for each exoplanet. The first target was the test case WASP-75b for which a rudimentary data reduction and analysis procedure resulted in a transmission spectrum of a low precision. The data set for this target was mainly used for practice purposes and so the analysis is brief. The next target was the low-density hot Saturn WASP-88b. Here, I examined a polynomial detrending approach and a detrending approach based on Gaussian Processes (GPs) in an effort to isolate the systematic effects from the transit light curves. The resulting transmission spectrum was found to be featureless with atmospheric models indicating the presence of high-altitude haze. The final target was the hot Jupiter WASP-74b. In this case, a new method that performs a common-mode correction only to the light curves of the target and considers an exponential of airmass during GP detrending was also presented in the spectroscopic analysis. This method resulted in increased transit depth precision and a steep scattering slope in the measured blue-optical transmission spectrum that suggests enhanced haze in the upper atmosphere. The results for WASP-88b and WASP-74b are representative of an emerging trend of steep scattering slopes observed in an increasing number of exoplanet atmospheres. The physics behind this spectral shape is not yet well-understood but several mechanisms have been proposed