Javier Lacasta

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.

On the problem of identifying the quality of geographic metadata

Geographic metadata quality is one of the most important aspects on the performance of Geographic Digital Libraries. After reviewing previous attempts outside the geographic domain, this paper presents early results from a series of experiments for the development of a quantitative method for quality assessment. The methodology is developed through two phases. Firstly, a list of geographic quality criteria is compiled from several experts of the area. Secondly, a statistical analysis (by developing a Principal Component Analysis) of a selection of geographic metadata record sets is performed in order to discover the features which correlate with good geographic metadata.

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.

Editorial: Design and evaluation of a semantic enrichment process for bibliographic databases

The limited semantics of thesauri and similar knowledge models hinder the searching and browsing possibilities of the bibliographic databases classified with this type of resource. This work proposes an automatic process to convert a knowledge model into a domain ontology through the alignment with DOLCE, an upper level ontology. This process is facilitated by an intermediary alignment with WordNet, a lexical model. The process has been tested with the thesauri and bibliographic databases of Urbamet and the European Urban Knowledge Network. The Urbamet model has been used to create an atlas of urban related resources with advanced search capabilities.

An ontology for the representation of spatiotemporal jurisdictional domains in information retrieval systems

Jurisdictional domains are generally accepted political divisions of the earth surface that cover specific territorial and functional scopes over time. They are frequently used in information retrieval (IR) to classify and locate resources by means of their geographical location. However, the changes they suffer over time reduce their applicability in historical collections. In this context, and with the objective of improving the use of jurisdictional domains, this article proposes an ontology schema that combines in a single model the administrative structure, the spatial components, and the temporal evolution of jurisdictional domains. This ontology schema has been used to create the Spanish jurisdictional model. Additionally, as an example of its applicability in the IR context, the Spanish model has been used as part of a location-based query component for the Spanish Official State Gazette.

Exploiting Disambiguated Thesauri for Information Retrieval in Metadata Catalogs

Information in Digital Libraries is explicitly organized, described, and managed. The content of their data resources is summarized into small descriptions, usually called metadata, which can be either introduced manually or automatically generated. In this context, specialized thesauri are frequently used to provide accurate content for subject or keyword metadata elements. However, if a Digital Library aims at providing access for the general public, it is not reasonable to assume that casual users will use the same terms as the keywords used in metadata records. As an initial step to fill the semantic gap between user queries and metadata records, the authors of this paper already created a method for the semantic disambiguation of thesauri with respect to an upper-level ontology (WordNet). This paper presents now the integration of this disambiguation within an information retrieval system, in this case adapting the vector-space retrieval model. Thanks to the disambiguation, both metadata records and queries can be homogenously represented as a collection of WordNet synsets, thus enabling the computing of a similarity value, which ranks the results.

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.

Improving the geospatial consistency of digital libraries metadata

Consistency is an essential aspect of the quality of metadata. Inconsistent metadata records are harmful: given a themed query, the set of retrieved metadata records would contain descriptions of unrelated or irrelevant resources, and may even not contain some resources considered obvious. This is even worse when the description of the location is inconsistent. Inconsistent spatial descriptions may yield invisible or hidden geographical resources that cannot be retrieved by means of spatially themed queries. Therefore, ensuring spatial consistency should be a primary goal when reusing, sharing and developing georeferenced digital collections. We present a methodology able to detect geospatial inconsistencies in metadata collections based on the combination of spatial ranking, reverse geocoding, geographic knowledge organization systems and information-retrieval techniques. This methodology has been applied to a collection of metadata records describing maps and atlases belonging to the Library of Congress. The proposed approach was able to automatically identify inconsistent metadata records (870 out of 10,575) and propose fixes to most of them (91.5%) These results support the ability of the proposed methodology to assess the impact of spatial inconsistency in the retrievability and visibility of metadata records and improve their spatial consistency.

Identifying hidden geospatial resources in catalogues

Geonetwork systems are one of the most popular geographic resources catalogues on the Web. One of the key elements of the successful of Geonetwork is the Geospatial metadata. Geonetwork use the direct and indirect spatial references from the metadata to process the spatial queries. However the inconsistencies between direct and indirect spatial references generate imprecise results, the invisibility of potential resources, and consequently the omission of many important data. The visibility of resources in a collection often depends on the consistency of the descriptions that help to find resources. Spatially inconsistent metadata records can hide resources and make them irretrievable. This paper presents an automatic method based on the combination of spatial clustering, reverse geocoding, and information retrieval techniques able to measure and detect geosemantic inconsistencies in metadata collections. Experimental results with a large metadata dataset about Geospatial Web Services show that the use of this method provides not only significant advantage in terms of accuracy, but also a gain of geosemantic insight into the metadata. Approach like this could be used by semantic technologies to draw connection from unstructured geospatial information to data from other structured geospatial information.