José Ramon Rios Viqueira

SQL extension for spatio-temporal data

An SQL extension is formalized for the management of spatio-temporal data, i.e. of spatial data that evolves with respect to time. The extension is dedicated to applications such as topography, cartography, and cadastral systems, hence it considers discrete changes both in space and in time. It is based on the rigid formalization of data types and of SQL constructs. Data types are defined in terms of time and spatial quanta. The SQL constructs are defined in terms of a kernel of few relational algebra operations, composed of the well-known operations of the 1NF model and of two more, Unfold and Fold. In conjunction with previous work, it enables the uniform management of 1NF structures that may contain not only spatio-temporal but also either purely temporal or purely spatial or conventional data. The syntax and semantics of the extension is fully consistent with the {SQL:2003} standard.

A generic framework for GIS applications

Geographic information systems (GIS) are becoming more usual due to the improved performance of computer systems. GIS applications are being developed using the three-tier software architecture traditionally used for general-purpose information systems. Even though this architecture is suitable for GIS applications, the special nature and exclusive characteristics of geographic information pose special functional requirements on the architecture in terms of conceptual and logical models, data structures, access methods, analysis techniques, or visualization procedures. In this paper, we propose a generic architecture for GIS that provides support for the special nature of geographic information and conforms with the specifications proposed by the ISO/TC 211 and the OGC. Our strategy to achieve this goal consists of two steps: (i) we analyze the special characteristics of GIS with respect to traditional information systems, (ii) and we adapt the traditional three-tier architecture for information systems to take into account the special characteristics of GIS. Finally, we have tried to apply the architecture that we propose in the development of a complete and complex real-life GIS application using commercial tools in the analysis, design and implementation. We describe this application, and we use it to describe the limitations of current commercial GIS development tools by analyzing the differences in the architecture of the resulting system with respect to our proposal.

Virtual integration of sensor observation data

This paper discusses the design, implementation and evaluation of a framework that enables the virtual integration of heterogeneous observation data sources through a Sensor Observation Service (SOS) standard interface. Currently available SOS implementations follow a data warehouse design approach for data integration. Contrary to this, the present framework uses a well-known Mediator/Wrapper virtual data integration architecture, enabling the direct access to the current data supplied by the data sources. Currently, the framework is being validated as the OGC compliant technology to publish the meteorological and oceanographic observation data generated by two public agencies of the regional government of Galicia (Northwest of Spain). HighlightsVirtual observation data integration vs. prevailing data warehouse approaches.Flexible combination of Mediator/Wrapper architecture with OGC SWE interfaces.In situ and remote static and mobile sensors producing vector and raster data.Multi-thread implementation to leverage current hardware multicore architectures.Under validation in two Spanish public meteorological and oceanographic agencies.

Improving Accessibility of Web-Based GIS Applications

A major problem of vector active map formats such as WebCGM and scalable vector graphics (SVG) is that, in order to display them in most Web browsers, either a plug-in has to be installed or an applet has to be downloaded. In this paper, a Web service is presented whose functionality enables the transformation of vector active maps from SVG to a new DHTML (HTML+JavaScript) active map representation, improving this way the accessibility of Web-based GIS applications. This new representation, which is also part of the present work, includes a raster representation of the map and a vector representation of its geographic objects. The former is used as a background image of the map whereas the latter enables the response to user-triggered events. An R-tree spatial index structure is used to access the geographic objects affected by each event in order to execute the relevant action

Using geographical information systems to browse touristic information.

The current expansion of Internet makes it one of the most popular places to publish and search for almost any kind of information. In particular, touristic information, not only about tours or information about resources, places, museums or monuments, but also cultural tourism, has gained much attention in the last years. We propose the use of geographical information systems technology (GIS) that provides interfaces capable of displaying interactive maps with information associated to the elements present in such maps. In this paper, we present a Web interface to access touristic information about Galicia (Spain) using GIS technology to easily find any touristic or cultural information. This interface is enclosed in the Galician Virtual Library (http://bvg.udc.es) Web site.

GeoDADIS: A framework for the development of geographic data acquisition and dissemination servers

The homogeneous access to sensor data in data monitoring and analysis applications is gaining much interest nowadays. To tackle this problem from an application independent perspective, the design and implementation of a framework called GeoDADIS for the development of data acquisition and dissemination servers is discussed in the present paper. Those servers are of common use in monitoring applications as they perform as gateways between decision support and data visualization technologies used in application developments and the heterogeneous collection of protocols and interfaces available in the industrial area for sensor data access. To achieve its objective, the architecture of GeoDADIS consists of: (i) a bottommost data acquisition layer that communicates with sensors, (ii) a middle kernel layer that provides general purpose functionality related to data management and system control and (iii) a topmost external interaction layer that enables the access from applications. The frameworks design does extensive use of the adapter (wrapper) design pattern to ease the incorporation of new data acquisition channels at the data acquisition layer and new data and remote control services in the external interaction layer. This makes GeoDADIS a very flexible and general purpose tool with broad application in many data monitoring domains.

An Index Structure To Retrieve Documents With Geographic Information

Optimal sensor placement is one that maximizes the likelihood of identifying future damage models. Based on assumptions from engineers, damage models of a structure are simulated and their predictions are computed. Computational approaches are used to place sensors at locations that maximize the chances of identifying damage. This paper studies the application of global search for optimal sensor placement. The global search methodology uses stochastic sampling to find optimal locations for sensors. In a previous study, Robert-Nicoud et al. proposed a greedy strategy that places sensors sequentially at locations where model predictions have maximum entropy. Performance of the two strategies are compared for the Schwandbach bridge in Switzerland. The results show that global search is better for designing measurement systems on a previously unmonitored structure while the greedy algorithm is better for incremental measurement- interpretation strategies.Both geographic information systems and information retrieval have been very active research fields in the last decades. Lately, a new research field called geographic information retrieval has appeared from the intersection of these two fields. The main goal of this field is to define index structures and techniques to efficiently store and retrieve documents using both the text and the geographic references contained within the text. We present in this paper the architecture of a system for geographic information retrieval. It defines a workflow for the extraction of the geographic references in the document. In addition, a new index structure is defined that combines an inverted index, a spatial index, and an ontology. This structure improves the query capabilities of other proposals.

Managing a Geographic Database from Mobile Devices Through OGC Web Services

We present in this paper a system for the management of geographic databases from mobile devices. The architecture of the system is extensible in the sense that it can be adapted to the particular characteristics of a wide variety of heterogenous mobile devices. This is achieved by the incorporation of an extensible middleware between the limited GIS applications running at the Mobile devices and the general purpose web services used at the data tier. The interfaces of these web services are compliant with the well-known Web Map Service(WMS) and Web Feature Service (WFS) specifications proposed by the Open Geospatial Consortium (OGC). A first prototype of the system for a specific PDA hardware with a specific software configuration was also implemented. We believe that the system has many practical applications in wireless environments with connectivity problems.

Spatio-temporal SQL

An extension of SQL is formalized for the management of spatio-temporal data, i.e. of spatial data that evolves with respect to time. The syntax and semantics of the extension is fully consistent with SQL. The formalism is very general, in that the extension can be applied to any kind of data, either temporal or spatial or conventional.

Sensor Observation Service Semantic Mediation: Generic Wrappers for In-Situ and Remote Devices

In-situ and remote sensors produce data that fit different data modeling paradigms, namely, Entity/Relationship paradigm for the former and Multidimensional Array paradigm for the latter. Besides, different standardized data access services are used in practice. Therefore their integrated access is still a major challenge. This paper describes a solution for the development of generic semantic data access wrappers for observation datasets generated by in-situ and remote sensing devices. Those wrappers are key components of data mediation architectures designed for the semantic integrated publishing of observation data.