Gene Expression Arrays
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Gazetteers L INDA L. H ILL University of California-Santa Barbara, Santa Barbara, CA, USA
Synonyms Place names; Toponyms; Knowledge organization systems; Ontologies
Definition A simple definition is that gazetteers are dictionaries of placenames. The digital gazetteer as a component of georeferenced information systems, however, is more formally modeled. A gazetteer is defined as a collection of gazetteer entries, each of which contains, at a minimum, the tuple N, F, T where N is a place name, F is a formal expression of geographic location – a footprint, and T is a place type expressed with a term (or code) from a typing scheme. Applications often require, in addition, relationships between gazetteer entries, documentation of time frames, and additional information (as described below). The gazetteer model is a type of knowledge organization system (KOS) – or ontology – which can be modified to represent other classes of spatial-temporal information, such as named time periods and named events [3].
Key Points Gazetteers support bidirectional translation between informal georeferencing using names (e.g., Las Vegas) and formal georeferencing using coordinates (e.g.,
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36 100 3000 N, 115 080 1100 W) or similar mathematical reference within a geospatial framework. The need for such translation is common, For example, to calculate routes and distances and to support information retrieval by either place names or coordinates. A common use for gazetteers is to answer the ‘‘where is’’ question: ‘‘where is Baltimore?’’ can be answered by a map display showing the locations of places called ‘‘Baltimore’’ in the world. In addition to place names and geospatial location, a third basic component of a gazetteer entry is a classification according to a typing scheme; that is, assigning a type term to a place to indicate that it is a populated place, a river, an island, a country, a bank, etc. There is no single typing scheme for named places. Instead, there are multiple typing schemes, usually unique for a particular application. All of the descriptive data associated with named places have time dimensions. To deal with these temporal dimensions adequately, a gazetteer data structure must incorporate time ranges for places as well as for most of the elements of description. Since different names can be used for the same place (e.g., in multiple languages), gazetteers must support multiple names and, ideally, document the source and time frame of each name. Supporting multiple footprints and information about a place from multiple sources is also needed for some applications. A gazetteer is a collection of gazetteer entries [5]. Inherent spatial relationships exist between gazetteer entries. It can be determined which places are located within the footprint of another place – at least, theoretically. Actually, the ability to do this adequately depends on the quality of the footprints. Explicit relationships between gazetteer entries can also be added to the descriptive information.
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