Clodoveu A. Davis

Ontologies and Knowledge Sharing in Urban GIS

Data and knowledge exchange among users of urban information systems presents many challenges. This paper discusses issues related to the use of ontologies in the development of urban geographic information systems and proposes the creation of software components from diverse ontologies as a way to share knowledge and data. These software components are derived from ontologies using an object-oriented mapping. The translation of an ontology into an active information system component leads to ontology-driven information systems and, in the specific case of geographic applications, to ontology-driven geographic information systems. We analyze the urban environment from the ontologists point of view and make some inferences about the relationship between knowledge and data sharing, and the theory of bona fide and fiat objects. We also discuss implementation issues, such as the use of Ontolingua as an ontology editor, and CORBA IDL generator, CORBA, and Java as object platforms.

OMT-G: An Object-Oriented Data Model for Geographic Applications

Semantic and object-oriented data models, such as ER, OMT, IFO, and others, have been extensively used for modeling geographic applications. Despite their semantic expressiveness, such models present limitations to adequately model those applications, since they do not provide appropriate primitives for representing spatial data. This paper presents OMT-G, an object oriented data model for geographic applications. OMT-G provides primitives for modeling the geometry and the topology of spatial data, supporting different topological structures, multiple views of objects, and spatial relationships. OMT-G also includes tools to specify transformation processes and presentation alternatives, that allow, among many other possibilities, modeling for multiple representations and multiple presentations. In this way, it overcomes the main limitations of the existing models, thus providing more adequate tools for modeling geographic applications. A comparison with other data models is also presented in order to stress the main advantages of OMT-G.

Assessing the Certainty of Locations Produced by an Address Geocoding System

Addresses are the most common georeferencing resource people use to communicate to others a location within a city. Urban GIS applications that receive data directly from citizens, or from legacy information systems, need to be able to quickly and efficiently obtain a spatial location from addresses. In this paper we understand addresses in a broader perspective, in which not only the conventional elements of postal addresses are considered, but other kinds of direct or indirect references to places, such as building names, postal codes, or telephone area codes, which are also valuable as locators to urban places. This broader view on addresses allows us to work with two perspectives. First, in the ontological definition, modeling, and implementation of an addressing database that is flexible enough to accommodate the variety of concepts and address formats used worldwide, along with direct and indirect references to places. Second, in the definition of an indicator that is able to quantify the degree of certainty that could be reached when a user-given, semi-structured address is geocoded into a spatial position, as a function of the type and completeness of the available addressing data and of the geocoding method that has been employed. This indicator, which we call Geocoding Certainty Indicator (GCI), can be used as a threshold, beyond which the geocoded event should be left out of any statistical analysis, or as a weight that allows spatial analysis methods to reduce the influence of events that have been less reliably located. In order to support geocoding activities and the determination of the GCI, we propose a conceptual schema for addressing databases. The schema is flexible enough to accommodate a variety of addressing systems, at various levels of detail, and in different countries. Our intention is to depart from the usual geocoding strategy employed in commercial GIS products, which is usually limited to the average American or British address format. The schema also extends the notion of postal address to something broader, including popular names for places, building names, reference places, and other concepts. This approach extends Simpson’s and Yu’s Comput. Environ. Urban Syst., 27: 283–307, 2003 work on postal codes to records of any kind, including place names and loosely formatted addresses.

Spatial data integrity constraints in object oriented geographic data modeling

An important activity in the design of a particular database application consists in identifying the integrity constraints that must hold on the database, and that are used to detect and evaluate inconsistencies. It is possible to improve data quality by imposing constraints upon data entered into the database. These constraints must be identified and recorded at the database design level. However, it is clear that modeling geographic data requires models which are more specific and capable of capturing the semantics of geographic data. Within a geographic context, topological relations and other spatial relationships are fundamentally important in the definition of spatial integrity rules. This paper discusses the relationship that exists between the nature of spatial information, spatial relationships, and spatial integrity constraints, and proposes the use of OMT-G, an extension of the OMT model for geographic applications, at an early stage in the specification of integrity constraints in spatial databases. OMT-G provides adequate primitives for representing spatial data, supports spatial relationships, and allows topological, semantic and user integrity rules to be specified in the database schema.

Semantic Expansion of Geographic Web Queries Based on Natural Language Positioning Expressions

The need for better Web search tools is getting increasing attention nowadays. About 20% of the queries currently submitted to search engines include geographic references. Thus, it is particularly important to work with the semantics of such queries, both by understanding the terminology and by recognizing geographic references in natural language text. In this paper, we explore the use of natural language expressions, which we call positioning expressions , to perform geographic searches on the Web, without resorting to geocoded data or gazetteers. Such positioning expressions denote the location of a subject of interest with respect to a landmark. Our approach leads to a query expansion technique that can be explored by virtually any keyword-based search engine. Results obtained in our experiments show an expressive improvement over the traditional keyword-based search and a potential path for tackling many kinds of common geographic queries.

Multiple representations in GIS: materialization through map generalization, geometric, and spatial analysis operations

Geographic information systems (GIS) deal with data which can potentially be useful for a wide range of applications. However, the information needs of each application usually vary, specially in resolution, detail level, and representation style, as defined in the modeling phase of the geographic database design. To be able to deal with such diverse needs, GIS must offer features that allow multiple representations for each geographic entity of phenomenon. This paper presents a framework for the implementation of multiple representations in GIS with minimum data redundancy, based on a comprehensive set of basic operators from computational geometry, spatial analysis, and map generalization. These operators are used to transform a representation into another, or to generate various presentations from a given representation.

An ontological gazetteer and its application for place name disambiguation in text

The volume of spatial information on the Web grows daily, both in the form of online maps and as references to places embedded in documents and pages. Considering the spatial information needs of users, it is often necessary to recognize, within a document’s text, the places to which it refers. This article presents a next-generation gazetteer, a toponymic dictionary which expands from the traditional cataloguing of place names and includes geographic elements such as spatial relationships, concepts and terms related to places. As such, we call it an OntoGazetteer, i.e., a gazetteer which also records semantic connections among places. The ontological gazetteer provides factual and semantic support to solving several common problems in geographic information retrieval. This paper presents the OntoGazetteer and demonstrates its applicability to a place name disambiguation problem. Along with other problem solutions to which the OntoGazetteer can contribute, we present a case study on recognizing and disambiguating place names within news sources.

Improving geographic information retrieval in spatial data infrastructures

In recent years, spatial data infrastructures (SDIs) have gained great popularity as a solution to facilitate interoperable access to geospatial data offered by different agencies. In order to enhance the data retrieval process, current infrastructures usually offer a catalog service. Nevertheless, such catalog services still have important limitations that make it difficult for users to find the geospatial data that they are interested in. Some current catalog drawbacks include the use of a single record to describe all the feature types offered by a service, the lack of formal means to describe the semantics of the underlying data, and the lack of an effective ranking metric to organize the results retrieved from a query. Aiming to overcome these limitations, this article proposes SESDI (Semantically-Enabled Spatial Data Infrastructures), which is framework that reuses techniques of classic information retrieval to improve geographic data retrieval in a SDI. Moreover, the framework proposes several ranking metrics to solve spatial, semantic, temporal and multidimensional queries.

Planning the acoustic urban environment: a GIS-centered approach

The economic development taking place in large urban centers can often provide an improvement in life quality as a consequence of the wider availability of services. However, severe environmental problems can also occur, if a coordinated strategy involving adequate monitoring of established businesses is not carried out. Adequate assessment of the environmental impact which may result from the economic development can only be carried out if suitable tools are available to the administrators, enabling proper supervision of land occupation. Noise is a major source of nuisance in urban environments, and in general 70% of the inhabitants of large cities usually describe noise related disturbances as a very important factor affecting life quality. This paper describes a set of GIS-based tools intended to provide the administrators with a methodology enabling a proper assessment of the acoustic impact within the urban environment. A model establishing the correlation between the spatial distribution of impacts and the relevant activities is developed. This model has been implemented as a prototype in a GIS environment, using Belo Horizonte’s geographic database, which is intended to represent a typical large Brazilian city situation. Initial field measurements compare favorably with this prototype, indicating the feasibility of the proposed approach.

Geographical Information Engineering in the 21st Century

This paper discusses the challenges facing GIS designers in the 21st century. We argue that GI engineers lack a sound theoretical basis that would allow them to make best use of new technologies that handle geospatial data. Considering three important topics for the new generations of GIS (change, semantics, and cognition) we show that GIS theory is in a state of flux. Thus, researchers and engineers need to cooperate more for the new generation of GIS to be built in the best possible way.