XQOWL: An Extension of XQuery for OWL Querying and Reasoning

One of the main aims of the so-called Web of Data is to be able to handle heterogeneous resources where data can be expressed in either XML or RDF. The design of programming languages able to handle both XML and RDF data is a key target in this context. In this paper we present a framework called XQOWL that makes possible to handle XML and RDF/OWL data with XQuery. XQOWL can be considered as an extension of the XQuery language that connects XQuery with SPARQL and OWL reasoners. XQOWL embeds SPARQL queries (via Jena SPARQL engine) in XQuery and enables to make calls to OWL reasoners (HermiT, Pellet and FaCT++) from XQuery. It permits to combine queries against XML and RDF/OWL resources as well as to reason with RDF/OWL data. Therefore input data can be either XML or RDF/OWL and output data can be formatted in XML (also using RDF/OWL XML serialization).Comment: In Proceedings PROLE 2014, arXiv:1501.0169

Querying and reasoning with RDF(S)/OWL in XQuery

Abstract. In this paper we investigate how to use the XQuery language for querying and reasoning with RDF(S)/OWL-style ontologies. Our proposal allows the handling of RDF(S)/OWL triples by means of a XQuery library for the Semantic Web, and it encodes RDF(S)/OWL reasoning by means of XQuery functions. We have tested and implemented the approach

PTL: A Model Transformation Language based on Logic Programming

In this paper we present a model transformation language based on logic programming. The language, called PTL (Prolog based Transformation Language), can be considered as a hybrid language in which ATL (Atlas Transformation Language)-style rules are combined with logic rules for defining transformations. ATL-style rules are used to define mappings from source models to target models while logic rules are used as helpers. The implementation of PTL is based on the encoding of the ATL-style rules by Prolog rules. Thus, PTL makes use of Prolog as a transformation engine. We have provided a declarative semantics to PTL and proved the semantics equivalent to the encoded program. We have studied an encoding of OCL (Object Constraint Language) with Prolog goals in order to map ATL to PTL. Thus a subset of PTL can be considered equivalent to a subset of ATL. The proposed language can be also used for model validation, that is, for checking constraints on models and transformations. We have equipped our language with debugging and tracing capabilities which help developers to detect programming errors in PTL rules. Additionally, we have developed an Eclipse plugin for editing PTL programs, as well as for debugging, tracing and validation. Finally, we have evaluated the language with several transformation examples as well as tested the performance with large models

XQuery Optimization Based on Program Slicing *

ABSTRACT XQuery has become the standard query language for XML. The efforts put on this language have produced mature and efficient implementations of XQuery processors. However, in practice the efficiency of XQuery programs is strongly dependent on the ability of the programmer to combine different queries which often affect several XML sources that in turn can be distributed in different branches of the organization. Therefore, techniques to reduce the amount of data loaded and also to reduce the intermediate structures computed by queries is a necessity. In this work we propose a novel technique that allows the programmer to automatically optimize a query in such a way that unnecessary intermediate computations are avoided, and, in addition, it identifies the paths in the source XML documents that are really required to resolve the query

Detecting and Diagnosing Syntactic and Semantic Errors in SPARQL Queries

ABSTRACT In this paper we present a tool to syntactically and semantically validate SPARQL queries. With this aim, we extract triple patterns and filter conditions from SPARQL queries and we use the OWL API and an OWL ontology reasoner in order to detect wrong expressions. Given an ontology and a query, the tool reports di↵erent kinds of programming errors: wrong use of vocabulary, wrong use of resources and literals, wrong filter conditions and wrong use of variables in triple patterns and filter conditions. When the OWL ontology reasoner is used the tool reports a diagnosis

OBIA System for Identifying Mesoscale Oceanic Structures in SeaWiFS and MODIS-Aqua Images

The ocean covers over 70% of the surface of our planet and plays a key role in the global climate. Most ocean circulation is mesoscale (scales of 50–500 km and 10–100 days), and the energy in mesoscale circulation is at least one order of magnitude greater than general circulation; therefore, the study of mesoscale oceanic structures (MOS) is crucial to ocean dynamics, making it especially useful for analyzing global changes. The detection of MOS, such as upwellings or eddies, from satellites images is significant for marine environmental studies and coastal resource management. In this paper, we present an object-based image analysis (OBIA) system which segments and classifies regions contained in sea-viewing field-of-view sensor (SeaWiFS) and Moderate Resolution Imaging Spectro-radiometer (MODIS)-Aqua sensor satellite images into MOS. After color clustering and hierarchical data format (HDF) file processing, the OBIA system segments images and extracts image descriptors, producing primary regions. Then, it merges regions, recalculating image descriptors for MOS identification and definition. First, regions are labeled by a human-expert, who identifies MOS: upwellings, eddies, cool, and warm eddies. Labeled regions are then classified by learning algorithms (i.e., decision tree, Bayesian network, artificial neural network, genetic algorithm, and near neighbor algorithm) from selected features. Finally, the OBIA system enables images to be queried from the user interface and retrieved by means of fuzzy descriptors and oceanic structures. We tested our system with images from the Canary Islands and the North West African coast

A location-based approach to the classification of mesoscale oceanic structures in SeaWiFS and Aqua-MODIS images of Northwest Africa

This study presents a different approach to the classification of Mesoscale Oceanic Structures (MOS) present in the Northwest African area, based on their location. The main improvement stems from the partition of this area in four large zones perfectly differentiated by their morphological characteristics, with attention to seafloor topography and coastal relief. This decomposition makes it easier to recognize structures under adverse conditions, basically the presence of clouds partly hiding them. This is observed particularly well in upwellings, which are usually very large structures with a different morphology and genesis in each zone. This approach not only improves the classification of the upwellings, but also makes it possible to analyse changes in the MOS over time, thereby improving the prediction of its morphological evolution. To identify and label the MOS classified in the Sea-viewing Wide Field-of-view Sensor (SeaWiFS) and Aqua-MODIS (Moderate Resolution Imaging Spectroradiometer) chlorophyll-a and temperature images, we used a tool specifically designed by our group for this purpose and which has again shown its validity in this new proposal

Metamorphic testing of OpenStreetMap

Context: OpenStreetMap represents a collaborative effort of many different and unrelated users to create a free map of the world. Although contributors follow some general guidelines, unsupervised additions are prone to include erroneous information. Unfortunately, it is impossible to automatically detect most of these issues because there does not exist an oracle to evaluate whether the information is correct or not. Metamorphic testing has shown to be very useful in assessing the correctness of very heterogeneous artifacts when oracles are not available. Objective: The main goal of our work is to provide a (fully implemented) framework, based on metamorphic testing, that will support the analysis of the information provided in OpenStreetMap with the goal of detecting faulty information. Method: We defined a general metamorphic testing framework to deal with OpenStreetMap. We identified a set of good metamorphic relations. In order to have as much automation as possible, we paid special attention to the automatic selection of follow-up inputs because they are fundamental to diminish manual testing. In order to assess the usefulness of our framework, we applied it to analyze maps of four cities in different continents. The rationale is that we would be dealing with different problems created by different contributors. Results: We obtained experimental evidence that shows the potential value of our framework. The application of our framework to the analysis of the chosen cities revealed errors in all of them and in all the considered categories. Conclusion: The experiments showed the usefulness of our framework to identify potential issues in the information appearing in OpenStreetMap. Although our metamorphic relations are very helpful, future users of the framework might identify other relations to deal with specific situations not covered by our relations. Since we provide a general pattern to define metamorphic relations, it is relatively easy to extend the existing framework. In particular, since all our metamorphic relations are implemented and the code is freely available, users have a pattern to implement new relations

2011): A Prolog library for OWL RL

ABSTRACT In this paper we describe the development of a Prolog library for OWL RL. OWL RL has been recently proposed by the W3C consortium as a fragment of OWL 2 for which reasoning can be done efficiently. In this context, we have studied how to implement a Prolog library based on OWL RL. By means of Prolog rules we are able to infer new knowledge from a given ontology. The OWL RL library has been implemented under the SWI-Prolog interpreter and is based on the RDF library provided by the SWI-Prolog environment, in such a way that OWL triples are computed and stored in secondary memory