ISO Online Resources
As the World Wide Web has developed into a ubiquitous information source, links to on-line information and services have become a critical element in all metadata records. These links are treated very differently in the FGDC and ISO standards.
FGDC: In the FGDC, URLs are free text with no associated information. These can only be displayed as links to themselves. This works, to some extent, for simple URLs, but does not work well for the more complex URLs that are becoming more common.
ISO: In the ISO, URLs are CI_OnlineResource objects that include a rich set of fields for describing the on-line resource:
<i>CI_OnlineResource</i> + linkage : URL + protocol [0..1] : CharacterString + applicationProfile [0..1] : CharacterString + name [0..1] : CharacterString + description [0..1] : CharacterString + function [0..1] : CI_OnLineFunctionCode <I>CI_OnLineFunctionCode</i> + download + information + offlineAccess + order + search
Usage: On-line linkage elements exist in the FGDC Citation, the Metadata Extensions, and are generally used in the Network Resource Name element in the Standard Order Process section.
The ISO CI_OnlineResource is found in the CI_Contact, the MD_DigitalTransferOptions, and the MD_MetadataExtensionInformation elements.
The NOAAServer URLs in many NOAA metadata records illustrate how these new elements can be used. NOAAServer supported three types of URLs: MoreInfo, Browse, and Obtain. These element names reflect the functions for the URLs. In the ISO standard, the browse URL would be included in the metadata as a browse image. The MoreInfo and Obtain URLs would be done as CI_OnlineResources with names (titles), descriptions, and information or order functions.
<b>FGDC:</b> <onlink>http://www.ngdc.noaa.gov/seg/fliers/se-0801.shtml</onlink> <b>FGDC (with NOAA Supplemental):</b> <noaainfo> <entry>G01372</entry> <nsurls> <moreinfo>http://www.ngdc.noaa.gov/seg/fliers/se-0801.shtml</moreinfo> <preview>http://www.ngdc.noaa.gov/seg/hazard/slideset/39/39_thumbs.shtml</preview> <obtain>http://ols.nndc.noaa.gov/olstore.prodspecific?prodnum=G01372-SLI-A0001</obtain> </nsurls> </noaainfo> <b>ISO:</b> <OnLineRes> <linkage>http://www.ngdc.noaa.gov/seg/fliers/se-0801.shtml</linkage> <protocol>http</protocol> <orname>NGDC Geologic Hazards Photos Homepage</orname> <ordesc>NGDC maintains a collection of geologic hazards photographs, many of which are available as 35mm slide sets, as digital images on CD-ROM or on-line. Each slide set consists of 20 slides in color and/or black and white along with a separate booklet of captions.</ordesc> <orfunc>001</orfunc> </OnLineRes>
The new information in the ISO Online Resources allows much more meaningful displays of those links. This example from CLASS (http://www.class.noaa.gov) shows a number of classified links with titles and descriptions in the Identification Information section.