DCLite4G Vocabulary

This version:
http://dclite4g.xmlns.com/
Author:
Jo Walsh, Pedro Goncalves

This work is licensed under a Creative Commons License. This copyright applies to the DCLite4G vocabulary documentation and does not apply to the vocabulary terms, or technology. DCLite4G relies heavily on W3C's RDF technology, an open Web standard that can be freely used by anyone. The dclite4g namespace URL, http://dclite4g.xmlns.com/schema.rdf contains an OWL ontology showing the structure, providing where possible mappings to various metadata schemas


Abstract

This resource aims to provide a simple method of representing some properties of geographic data sets. The vocabulary is defined in RDF and OWL.

It is a minimal vocabulary intended for use in extending Dublin Core-based descriptions of geographic data with more specific properties for use in processing geodata.

For an overview of DCLite4G including links to its history and design decisions please see the DCLite4G wiki pages at the Open Source Geospatial Foundation


Usage

Following is an example of a simple RDF document describing a geographic data set.


<?xml version="1.0" encoding="utf-8"?>
<rdf:RDF
        xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
        xmlns:dc="http://purl.org/dc/elements/1.1/"
        xmlns:dct="http://purl.org/dc/terms/"
        xmlns:dclite4g="http://xmlns.com/2008/dclite4g#"
        xmlns:foaf="http://xmlns.com/foaf/spec/"
        xmlns:ical="http://www.w3.org/2002/12/cal/ical#">

 <dclite4g:Series rdf:about="http://www.example.com/series/example_series/">
    <dc:title>An Example Data Series</dc:title>
    <dc:abstract>Description of example series</dc:abstract>
    <dc:identifier>example_series_001p</dc:identifier>
    <dc:subject>example</dc:subject>
    <dc:contact rdf:resource="http://www.example.com/contact/" />
    <dclite4g:projection>EPSG:4326</dclite4g:projection>   
 </dclite4g:Series>

 <dclite4g:DataSet rdf:about="http://www.example.com/series/example_series/example_data_set/example_series_file1">
   <dclite4g:series rdf:resource="http://www.example.com/series/example_series/" />
   <!-- 
		By using a series reference it will inherit all the Series
		elements that aren't explicitly defined here 
	-->
   <dc:identifier>example_series_file1</dc:identifier>
   <ical:dtstart>1970-01-01 00:00:00</ical:dtstart>
   <ical:dtend>1970-01-01 23:59:59</ical:dtend>
   <dct:spatial>
   POLYGON ((-18.125 30.25, -18.125 46.0, 36.25 46.0, 36.25 30.25, -18.125 30.25))
   </dct:spatial>
 </dclite4g:DataSet>

 <dclite4g:Service rdf:about="http://www.example.com/series/example_service/">
    <dc:title>An Example Service that accepts as input Series 1 and Series 2 </dc:title>
    <dclite4g:series rdf:resource="http://www.example.com/series/example1/" />
    <dclite4g:series rdf:resource="http://www.example.com/series/example2/" />
   <!-- 
		By using series references it informs that the service is compatible 
		and accepts datasets belonging to the specified Series
	-->

	<dc:abstract>Description of example service </dc:abstract>
    <dc:identifier>example_service_001p</dc:identifier>
    <dc:subject>example</dc:subject>
    <dc:contact rdf:resource="http://www.example.com/contact/" />
 </dclite4g:Service>

</rdf:RDF>


Classes in this vocabulary

Name Description
DataSetA resource containing geographic information (type http://purl.org/dc/dcmitype/Dataset). It belongs and inherits the properties of a Series.
SeriesA collection of geographic information resources (DataSets). May be a sequence of temporal updates, or a collection of tiles comprising one composite dataset, or a number of different format representations of the same underlying data. (type http://purl.org/dc/dcmitype/Collection). All properties of this class are inherited by the DataSets.
ServiceA system that provides one or more functions. It accepts DataSets of a given number of Series (type http://purl.org/dc/dcmitype/Service).

Properties in this vocabulary

Name Domain Range Description
series rdfs:Resource http://xmlns.com/2008/dclite4g#DataSet http://xmlns.com/2008/dclite4g#Service Identifies a DataSet or similar resource as belonging to a Series. The DataSet will inherit all the Series elements that aren't explicitly overridden. For the service it indetifies the Series that the service supports
onlineResource rdfs:Resource http://xmlns.com/2008/dclite4g#DataSet http://xmlns.com/2008/dclite4g#Service A reference to an online resource which provides direct access to the data set
projection rdfs:Literal http://xmlns.com/2008/dclite4g#DataSet http://xmlns.com/2008/dclite4g#Series http://xmlns.com/2008/dclite4g#Service The spatial projection of a data set or series. A code as commonly understood to spatial databases and projection libraries, in 'issuer:identifier' format - for example, EPSG:4326
file format rdfs:Literal http://xmlns.com/2008/dclite4g#DataSet http://xmlns.com/2008/dclite4g#Series http://xmlns.com/2008/dclite4g#Service A text string identifying the format in which data is being made available. E.g. 'netCDF', 'GML'. http://dclite4g.xmlns.com/formats.txt contains a list of recommended names for formats which can be identified by the 'gdalinfo' and 'ogrinfo' utilities (http://www.gdal.org/) If the source of the data is a service this would be, for example OGC:WMS or OGC:WCS.
scale rdfs:Literal http://xmlns.com/2008/dclite4g#DataSet http://xmlns.com/2008/dclite4g#Series http://xmlns.com/2008/dclite4g#Service Description of the scale of a data set or of a series of datasets at the same scale (e.g. 1:1000)
resolution rdfs:Literal http://xmlns.com/2008/dclite4g#DataSet http://xmlns.com/2008/dclite4g#Series http://xmlns.com/2008/dclite4g#Service Description of the resolution of the dataset, or a series of datasets at the same resolution
quicklook rdfs:Resource http://xmlns.com/2008/dclite4g#DataSet http://xmlns.com/2008/dclite4g#Series http://xmlns.com/2008/dclite4g#Service A reference to an online resource which provides direct access to a image quicklook of the dataset

Web Services vocabulary

The web services vocabulary supplements DCLite4G and is used to identify different kinds of protocols and services which are used to access geographic data. The vocabulary defines identifier URLs for different commonly-used services - WMS, WCS, LDAP, FTP among others. A dclite4g:onlineResource can contain one of these elements.

Dublin Core Subset elements to use with DClite4G

Name Card. Type Description
dc:identifier 1 URI A unique identifier which unambigiously identifies an item within a given context (i.e. a catalogue/repository, a model and a language) used for extracting and referencing metadata. Note also that this identifier is not necessary the identifier of a resource. To access the resource associated with a metadata record, one must use dclite4g:OnlineResource
dc:title 0..1 String A name given to the resource (regardless e.g. of naming restrictions of file systems. iso19128:title, iso19115: CI_Citation.title
dct:abstract 0..1 String A description of the resource. Either a URI reference to a human readable resource or a string. In case of dc:type 'service' (OWS) its the abstract (string) from of GetCapabilities document. iso19128:abstract, iso19115: MD_DataIdentification.abstract
dc:type 0..1 enumeration The nature or genre of the content of the resource. 'dataset' or 'service' else 'document, 'text', 'image', 'sound', etc. (see DCMI type controlled vocabulary - http://dublincore.org/documents/dcmi-type-vocabulary/ )
dc:format 0..1 URI A machine readable reference to either a internet media (mime) type (recommended) or a an xml schema namespace URI linking to an namespace authority. In case of dc:type='service' multiple schemas are to expect: insert them comma-separated
dct:spatial 0..1 String Well Known Text (WKT) string descriving the geometry to the resource
dct:created 0..1 date Date of the creation of resource (see W3C Encoding rules). Subtype of dc:date
dct:modified 0..1 date Date of last (published) change of resource (see W3C Encoding rules). Subtype of dc:date
dc:subject 0..1 string A keyword list; e.g. ISO 19115 classification list separated by comma.
dc:source 0..1 string Description from which the present resource is derived, lineage information. An URI reference to another resource (Note: Server base URLs and file URIs are handled elsewhere).
dc:publisher 0..1 string The entity responsible for making the resource available in its present form, such as a publishing house, a university department, or a corporate entity. This can be a reference to a foaf resource or civic address: if type service derived from GetCapabilities ('ContactInformation') else flattened KML style.
dc:language 0..1 enumeration RFC 1766 (ISO 639, followed optionally by country ISO 3166). Max. Cardinality is intentionally 1 which for the sake of simplicity means that translations of a metadata record in different languages is recorded in several metadata instances and not in multiple dc:language, dc:title or dct:abstract occurrences.
dc:rights 0..1 string License information link about the resource. Probably also (link to) disclaimers. Either an URI reference to a human readable resource or a string. It should use a controlled vocabulary or for an online definition of the license.

References

Acknowledgements

The name "DCLite4G" was coined by Stefan Keller, who also identified the need for a formalised way to extend Dublin Core / RSS / Atom-based feeds of geographic data with more detailed metadata properties.

Work on the refinement and use of the DCLite4G model has been supported by Terradue SRL. Terradue also kindly hosts the dclite4g.xmlns.com domain.

The style/layout of this document and the licensing information were adapted from the File Properties Vocabulary by Earle Martin, which in turn used the FOAF Vocabulary Specification by Dan Brickley and Libby Miller.


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