Marinos Kavouras

A method for the formalization and integration of geographical categorizations

In order to deal with semantic heterogeneity and achieve semantic interoperability between heterogeneous applications, it is necessary to formalize geographic knowledge. The present paper introduces a method to formalize and integrate different geographic categorizations. The method is based on the mathematical theory of Concept Lattices. These rich structures are used for managing multidimensional geographic categories and their overlapping relationships. The applicability of the method is tested on the problem of integrating different land cover/land use categorizations.

Fusion of top-level and geographical domain ontologies based on context formation and complementarity

This paper proposes a methodology for the fusion of different geographical domain ontologies with top-level ontologies, in order to provide a solid base for information exchange. The proposed methodology discusses context formation and the formalization of geographical concepts using essential properties.

An overview of 21 global and 43 regional land-cover mapping products

Land-cover (LC) products, especially at the regional and global scales, comprise essential data for a wide range of environmental studies affecting biodiversity, climate, and human health. This review builds on previous compartmentalized efforts by summarizing 23 global and 41 regional LC products. Characteristics related to spatial resolution, overall accuracy, time of data acquisition, sensor used, classification scheme and method, support for LC change detection, download location, and key corresponding references are provided. Operational limitations and uncertainties are discussed, mostly as a result of different original modelling outcomes. Upcoming products are presented and future prospects towards increasing usability of different LC products are offered. Despite the common realization of product usage by non-experts, the remote-sensing community has not fully addressed the challenge. Algorithmic development for the effective representation of inherent product limitations to facilitate proper usage by non-experts is necessary. Further emphasis should be placed on international coordination and harmonization initiatives for compatible LC product generation. We expect the applicability of current and future LC products to increase, especially as our environmental understanding increases through multi-temporal studies.

On the determination of the optimum path in space

Various algorithms have been proposed for the determination of the optimum paths in line networks. Moving in space is a far more complex problem, where research has been scarce. An example would be the determination of the shortest sea course between two given ports. This paper presents an examination of the problem, states the weaknesses of the existing solutions, and introduces a new approach, which can be easily applied to a variety of spaces, while considering different travel cost models. The implementation of the algorithm for movements on the plane surface, in the three-dimensional space, and on the spherical surface as an approximation of the earth, has been examined. The results are illustrated through several examples.

From “Onto-GeoNoesis” to “Onto-Genesis”: The Design of Geographic Ontologies

An important issue in geographic ontological research is the ability to design new ontologies. In this context, we first explore the desiderata of domain ontologies in terms of their constituting elements: i.e., the lexicon, concepts, relations, and axioms. Furthermore, we touch upon several characteristics of geographic concepts, which have puzzled geographic information scientists, and present critical topics of geographic ontological research. Based on the previous aspects of the problem, and guided by prior work of analyzing existent geographic ontologies, we have identified their qualities and deficiencies with regard to completeness and adequacy. This “meta-ontological” approach has guided us in presenting herein, a framework for generating robust geographic ontologies, which will comply with the semantics of the concepts of the specific domain.

Semantic information in geo-ontologies: extraction, comparison, and reconciliation

A crucial issue during semantic integration of different geographic metadata sources is category comparison and reconciliation. We focus on the development of a framework for identification and resolution of semantic heterogeneity between geographic categories. The framework is divided in three processes: extraction, comparison and reconciliation. The first process performs semantic information extraction and formalization based on definitions of geographic category terms. Definitions constitute important sources of semantic information for geographic categories. Based on specific rules, definitions are analyzed in a set of semantic elements (properties and values). This information is further used in the second process to identify similarities and heterogeneities between geographic categories. Heterogeneity reconciliation is implemented by semantic factoring, a conceptual analysis process which results in a set of non-redundant, non-overlapping categories.

Ontology assisted decision making – a case study in trip planning for tourism

Traditional trip planning involves decisions made by tourists in order to explore an environment, such as a geographic area, usually without having any prior knowledge or experience with it. Contemporary technological development has facilitated not only human mobility but also has set the path for various applications to assist tourists in way-finding, event notification using location-based services etc. Our approach explores how the use of ontologies can assist tourists plan their trip, in a web-based environment. The methodology consists of building two separate ontologies, one for the users profile and another one concerning tourism information and data in order to assist visitors of an area plan their visit.

Interoperability and definition of a national standard for geospatial data: the case of the Hellenic Cadastre

Abstract This study, evaluation and proposal of a standard suitable for the exchange of geographic data was conducted by the National Technical University of Athens as part of a research project on behalf of KTIMATOLOGIO S.A. and the Hellenic Mapping and Cadastral Organization. The primary application interest was the Hellenic Cadastre Project, which can be seen as a case-study of the role of standards, the functionality they provide, and their effects. The study reported relates mainly to theoretical and scientific issues of standardization. Several subjects were addressed during the process of selecting the standard and a series of evaluation criteria were formed. Three primary trends in standardization were considered, Open GIS, ISO/TC 211 and CEN/TC 287, and a generic-profile-product approach was pursued. The selected standard was DIGEST-C with a customized (and not modified) implementation version of an Urban VMap product. The customization process included the association of the schema available in the selected standard with the schema that have been used so far in Greece for cadastre applications. The utilization and implementation of the selected standard, intended to be a National Spatial Data Exchange Standard, has various implications, which are reported and evaluated.

Comparing representations of geographic knowledge expressed as conceptual graphs

Conceptual Graphs are a very powerful knowledge and meaning representation formalism grounded on deep philosophical, linguistic and object oriented principles [1], [2]. Concerning geographic knowledge representation and matching, the study and analysis of geographic concept definitions plays an important role in deriving systematic knowledge about concepts and comparing geographic categories in order to identify similarities and heterogeneities [4]. Based on the proposed algorithm for the representation of geographic knowledge using conceptual graphs, we also present a method that takes into consideration the special structure of conceptual graphs and produces an output that shows how much similar two geographic concepts are and hence which concept is semantically closer to another. For producing the conceptual graph representation of any geographic concept definition we follow two steps, tagging and parsing, while for measuring the similarity between two geographic ontologies we apply proper modifications to the Dice coefficient that is mainly used for comparing binary structures.

Spatial Concept Lattices: An Integration Method in Model Generalization

The ability to view and analyze data of different detail and from different perspectives, and to move dynamically from one scale to another requires modeling geographic information at different generalization levels. On this account, in the framework of model generalization, the concept of multi-scale database is adopted to provide a consistent multiple representation of existent mono-scale representations. Spatial Concept Lattices are propounded as a new approach to thematic generalization through the semantic integration of multiple classification schemata and the creation of a multi-scale, multi-context database. The methodology presents in an explicit and systematic manner the integration of classification schemata, which exhibit differences in spatial and thematic resolution. In order to comprehend the stepwise SCL methodology, an actual example is used to demonstrate the integration of three independent land cover/land use classification schemata. The integration process is part of model generalization, since the resulting hierarchical integrated schema supports various levels of thematic resolution and represents geographic space from different application perspectives.