Yassine Lassoued

Query processing in a geographic mediation system

Despite various interoperability recommendations, heterogeneity of Geographic Information Systems (GIS) is still an issue. This led to an increasing need for a data integration system that allows transparent and uniform access to spatial data disseminated over a network. In this paper, we describe the internals of query processing in the VirGIS mediation system. Recall that a data mediation system provides users with a uniform access to a multitude of (local/remote) data sources, without duplicating the data. The user poses his query against a virtual (global) schema, the query is in turn rewritten into queries sent to the local sources. VirGIS complies with Open GIS Consortium recommendations in using the Geography Markup Language (GML) for the encoding and the transport of geographic information, and the Web Feature Server (WFS) interfaces to perform communications with clients and data sources.

Towards similarity-based topological query languages

In recent times, the proliferation of spatial data on the Internet is beginning to allow a much larger audience to access and share data currently available in various Geographic Information Systems (GISs). Unfortunately, even if the user can potentially access a huge amount of data, often, she has not enough knowledge about the spatial domain she wants to query, resulting in a reduction of the quality of the query results. This aspect is even more relevant in integration architectures, where the user often specifies a global query over a global schema, without having knowledge about the specific local schemas over which the query has to be executed. In order to overcome such problem, a possible solution is to introduce some mechanism of query relaxation, by which approximated answers are returned to the user. In this paper, we consider the relaxation problem for spatial topological queries. In particular, we present some relaxed topological predicates and we show in which application contexts they can be significantly used. In order to make such predicates effectively usable, we discuss how GQuery, an XML-based spatial query language, can be extended to support similarity-based queries through the proposed operators.

COMMON SENSE: Cost-effective sensors, interoperable with international existing ocean observing systems, to meet EU policies requirements

The COMMON SENSE (CS) project aims to develop cost-effective, multi-functional innovative sensors to perform reliable in-situ measurements in the marine environment. The COMMON SENSE sensors will focus on key parameters including eutrophication, heavy metals, marine litter (microplastics) and underwater noise. The project will focus on increasing the availability of sensor data and observations through the development and implementation of the Common Sensor Web Platform (CSWP), a software platform that will integrate the COMMON SENSE sensor data and observations and deliver them to the Web, in standard formats and through standard interfaces.

GQBox: geospatial data quality assessment

In order to measure and assess the quality of GIS, there exist a sparse offer of tools, providing specific functions with their own interest but are not sufficient to deal with broader users requirements. Interoperability of these tools remains a technical challenge because of the heterogeneity of their models and access patterns. On the other side, quality analysts require more and more integration facilities that allow them to consolidate and aggregate multiple quality measures acquired from different observations or data sources, in using/combining seamlessly different quality tools. Clearly, there is a gap between userss requirements and the spatial data quality market. This demo paper will illustrate GQBox, a geographic quality (tool)box. GQBox supplies a standards-based generic meta model that supports the definition of quality goals and metrics, and it provides a service-based infrastructure that allows interoperability among several quality tools.

Processing Mediated Geographic Queries: a Space Partitioning Approach

In this paper, we address the objects’ fusion issue, in the context of a spatial data integration system. The issue consists in (1) identifying the “same” geographic objects coming from different data sources and, (2) joining their information in order to obtain one unified object with its complete information. We describe a query processing technique, based on space Partitioning, that allows reducing the objects fusion costs. The goal is to avoid useless join operations between objects that belong to different regions.

A metadata-driven geographic data mediator

Metadata are crucial for the development of Geographic Information Systems (GIS). With the availability of geographic data sources over the Web, assessing the fitness for use concept may become a tricky task. In this paper, we describe a metadata-driven mediation approach and system that allow a community of users to share a set of autonomous, heterogeneous and distributed geographic data sources with different metadata (quality) information. Users share a common vision of the data, which is defined by means of a global schema and a metadata schema. The paper shows how metadata (I) may provide efficiency, (2) improve semantic interoperability and (3) ensure fitness for use.