Geospatial Vocabulary
This page outlines a discussion about spatial vocabularies .
'Features' and 'Geometry' are common used terms in spatial vocabularies and describe two different concepts of geospatial science. A feature is simply an entity that can be affiliated with a location, but must not necessarily have a fixed position. A geometry is a geometric shape like a polygon, line, etc. and can be used to describe the spatial characteristics of a feature.
In this chapter different vocabularies for describing spatial data are evaluated in order to come to a conclusion, which ones are the most suitable for the cause of presenting the campus of a university including the indoor plans of buildings.
(source) Shortcut: geo
WGS84 is a basic vocabulary published by W3C to represent latitude, longitude and altitude information in the geodetic reference datum WGS84. It has a class for anything with spatial extent called SpatialThing. Spatial thing has one specified subclass called point.
The advantage of this vocabulary is that it is lightweight, but on the other side it is not suitable for describing more complex spatial data that is going beyond describing a simple point / spatial thing.
(source) Shortcut: schema
Schema is a vocabulary initiated by major search engines like Google, Yahoo, and Bing among others. The vocabulary itself is a collaborative, community-driven effort and is intended to be used for enriching websites with semantics so that the experience of certain services like search engines can be enhanced (because the content can be better understood with semantic annotations).
Schema.org has the class Place for entities that have a somewhat fixed, physical extension. The vocabulary includes a set of different places like CivicStructure, LocalBusiness, etc and properties to set these places in relationship with other entities like Events.
Properties for describing the position and geometry of places are important for the representation of geospatial data. Schema.org provides the property schema:geo for that. The object of this property is either a individual of the class GeoCoordinate or GeoShape. GeoCoordinate is similar to geo:point, but has properties to describe the address and locality respectively in addition to the shared long/lat/alt/ properties. GeoShape on the other side is a class to describe shapes as it could be guessed due to the name, but the way to describes shapes of places is quite restrictive. The property schema:box, schema:polygon, schema:line and schema:circle can be used to describe the form that is indicated by the name of the property. The description must be in textual form after a given pattern. The specification does not allow to describes shapes with GML, WKT or other forms of representation.
(source) Shortcut: geom
NeoGeo Geometry Ontology is vocabulary for describing geographical regions. In comparison to schema this vocabulary focuses on the representation of shapes and provides for this case a more comprehensive set of properties and classes. It also provides the possibility to present a Geometry entity in form of WKT. However, this property called asWKT is stated to be deprecated.
The advantage of this vocabulary is that more complex shapes (e.g. MultiPolygon, MultiLineString) can be presented in pure RDF without the need of using serializations like WKT, GML, etc.
(source) Shortcut: ogc
GeoSparql is not only a vocabulary for describing spatial data (features, geometries and their relationship), but also an attempt for standardizing the way spatial data can be queried using SPARQL to overcome the situation that different triple stores have different implementations. The two main classes of this vocabulary are Feature and Geometry.
(source) Shortcut: locn
ISA Programme Location Core Vocabulary focuses on describing the address and location of a given feature. It provides a minimum set of classes and properties for describing any place in terms of its name, address or geometry.
This vocabulary gives the designer the freedom to decide how (s)he wants to represent the Geometry of a place. The place can be put in relationship with the given Geometry by using the property locn:geometry. It is recommended that the Geometry object of this property is either a literal (e.g. WKT, GML) or a member of one of the following classes schema:GeoCoordinates, schema:GeoShape, and ogc:Geometry.
As a result this vocabulary can be used in combination with ogc or schema to describe the address and geometry of a place.
LinkedGeoData (link) is a project for providing spatial data collected by the community of OpenStreetMaps (link) as Linked Open Data. The vocabulary of LinkedGeoData uses the property ogc:asWTK to represent ways, buildings and other spatial entities in this format as well as the property geom:geometry for pointing to a geometrical representation geom:Geometry of a certain feature. Alongside the mentioned ones geo:lat and geo:long are also used.
University of Southampton (link) provides spatial data about the campus among other as Linked Open Data. In the provided linked data the properties geo:lat and geo:long are used to describe spatial points and dct:spatial to describe the geometry of buildings using WKT.