Francisco Javier Zarazaga-Soria

Metadata standard interoperability: application in the geographic information domain

Abstract The use of metadata expands on the opportunities for interoperability. Interoperability involves making multiple information sources access, manipulate and share data across their boundaries. Metadata descriptions from different domains are not semantically distinct but overlap and relate to each other in complex ways. As the number, size and complexity of the metadata standards grow, the task of facilitating metadata in different standards becomes more difficult and tedious. A possible solution for this problem is the creation of mechanisms that enable the translation of this information in order to make it conform to the different standards. These mechanisms are denominated “crosswalks” and the objective of this work is to present the process of “crosswalk-creation”, which has been used by a research team at the University of Zaragoza in order to translate information among some of the most extended standards for geographic information metadata.

A Web Ontology Service to facilitate interoperability within a Spatial Data Infrastructure: Applicability to discovery

Ontologies are used within the context of Spatial Data Infrastructures to denote a formally represented knowledge that is used to improve data sharing and information retrieval. Given the increasing relevance of semantic interoperability in this context, this work presents the specification and development of a Web Ontology Service (WOS), based on the OGC Web Service Architecture specification, whose purpose is to facilitate the management and use of lexical ontologies. Additionally, this work shows how to integrate this service with Spatial Data Infrastructure discovery components in order to obtain a better classification of resources and an improvement in information retrieval performance.

An architectural style for spatial data infrastructures

This work proposes an architectural style, a pattern, for spatial data infrastructures (SDIs). This style provides a tool and a shared vocabulary to help system architects to design these infrastructures, and facilitates the exchange of knowledge about them. This style is defined under the component‐and‐connector architectural viewtype, extending the client–server and shared‐data styles. The style has been created after analyzing six of the most relevant SDIs and geo‐service architectural proposals. Several architectural elements that these proposals have not properly addressed are considered. Three real projects, with published architectural views or models, have been examined to verify the applicability of the style. The proposed style offers a systematization and refinement of knowledge about SDIs, grounded in well‐known concepts in software architecture.

Administrative Units, an Ontological Perspective

The administrative units have been created with the purpose of covering specific territorial and functional scopes over time. Therefore, there are heterogeneity not only among states but also at any level of subdivision. In the context of Spatial Data Infrastructures, administrative units are part of the core data model and they are often exploited in the development of web services. International, cross-border, even national web services may face different and superposed administrative models. The administrative models are complex and they may not be well understood by users and developers in some scenarios, i.e. a query in boundary areas with different administrative models. This paper proposes an ontology that can describe administrative models and also serve as a knowledge base that may facilitate mappings between different types of administrative units.

An Approach to Facilitate the Integration of Hydrological Data by means of Ontologies and Multilingual Thesauri

The general concern about environmental issues has involved the creation of national and international policies that require, at a technical level, the analysis, merging and processing of data obtained from very different sources. This paper proposes an approach for the integration of hydrological data that is based on the use of a multilingual ontology to facilitate the mapping across the local data models in the different sources. The novelty of the proposal is that the multilingual domain ontology is generated automatically by the merging and pruning of existing lexical ontologies. This approach has been tested in the context of the European Water Framework directive for the development of reporting applications in cross-border scenarios. Nevertheless, this approach could be easily extended to other domains.

Semantic interoperability based on Dublin Core hierarchical one-to-one mappings

The tendency of current cataloguing systems is to interchange metadata in XML according to the specific standard required by each user on demand. Furthermore, metadata schemas from different domains are not usually semantically distinct but overlap and relate to each other in complex ways. As a consequence, the semantic interoperability has to deal with the equivalences between those descriptions. There exist two main approaches in order to tackle this problem: solutions based on the use of ontologies and solutions based on the creation of specific crosswalks for one-to-one mapping. This paper proposes a hierarchical one-to-one mapping solution for improving semantic interoperability.

Identifying orthoimages in Web Map Services

Orthoimages are essential in many Web applications to facilitate the background context that helps to understand other georeferenced information. Catalogues and service registries of Spatial Data Infrastructures do not necessarily register all the services providing access to imagery data on the Web, and it is not easy to automatically identify whether the data offered by a Web service are directly imagery data or not. This work presents a method for an automatic detection of the orthoimage layers offered by Web Map Services. The method combines two types of heuristics. The first one consists in analysing the text in the capabilities document. The second type is content-based heuristics, which analyse the content offered by the Web Map Service layers. These heuristics gather and analyse the colour features of a sample collection of image fragments that represent the offered content. An experiment has been performed over a set of Web Map Service layers, which have been fetched from a repository of capabilities documents gathered from the Web. This has proven the efficiency of the method (precision of 87% and recall of 60%). This functionality has been offered as a Web Processing Service, and it has been integrated within the Virtual Spain project to provide a catalogue of orthoimages and build realistic 3D views.

Building an Address Gazetteer on top of an Urban Network Ontology

In order to create the contents of an address gazetteer service that forms part of a city council Spatial Data Infrastructure, all the exis- tent repositories containing address information in the difierent council o-ces must be analyzed and harmonized. The problem is that usually these repositories are constrained by the use of difierent taxonomies for the identiflcation of urban network feature types. The objective of this work will be to describe how to establish a formal ontology enabling the interoperability among the difierent taxonomies, and facilitating the construction of the gazetteer contents.

SDI-based business processes: A territorial analysis web information system in Spain

Spatial Data Infrastructures (SDIs) provide access to geospatial data and operations through interoperable Web services. These data and operations can be chained to set up specialized geospatial business processes, and these processes can give support to different applications. End users can benefit from these applications, while experts can integrate the Web services in their own business processes and developments. This paper presents an SDI-based territorial analysis Web information system for Spain, which gives access to land cover, topography and elevation data, as well as to a number of interoperable geospatial operations by means of a Web Processing Service (WPS). Several examples illustrate how different territorial analysis business processes are supported. The system has been established by the Spanish National SDI (Infraestructura de Datos Espaciales de Espana, IDEE) both as an experimental platform for geoscientists and geoinformation system developers, and as a mechanism to contribute to the Spanish citizens knowledge about their territory.

Water Quality Monitoring to Support the European Commission's Water Framework Directive Reporting Requirements

This article aims at providing a simple way for water quality monitoring in a set of reservoirs using an earth observation-based approach and the assessment of the use of this technique for a monitoring network in order to meet the requirements and objectives of the Water Framework Directive (WFD) by the Member States of the European Union. The study carried out was preformed in 42 reservoirs of the Ebro River Basin, in the northeast of Spain. The proposed methodology is based on the development of an algorithm for the estimation of water quality by means of LANDSAT TM band reflectance. Some band ratios were used in the model as well. Trophic State Index (TSI), calculated by means of Secchi Disc Transparency data, was estimated using a forward stepwise multiple regression analysis and the TM2 band and TM1/TM2 ratio. The final results showed a large variability in water quality across reservoirs. Moreover, substantial spatial heterogeneity was also observed in the water bodies. These results demonstrate the likelihood of developing a monitoring network based on remote sensing techniques for the implementation of the WFD.