Difference between revisions of "Documenting Online Resources"

From Earth Science Information Partners (ESIP)
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#Types and Function Codes - All three dialects include a mechanism for classifying online resources. DIF and ISO use shared vocabularies and ECHO uses free text. The DIF vocabulary is hierarchical and includes roughly 35 choices. The ISO codeList includes 11 broad categories. The ECHO Collection metadata currently includes roughly 45 different values with some overlap with the DIF list. Given the variation in these existing approaches, it seems reasonable to map the DIF and ECHO types into the ISO name element, which is free text, rather than into the function element which is a codeList.
 
#Types and Function Codes - All three dialects include a mechanism for classifying online resources. DIF and ISO use shared vocabularies and ECHO uses free text. The DIF vocabulary is hierarchical and includes roughly 35 choices. The ISO codeList includes 11 broad categories. The ECHO Collection metadata currently includes roughly 45 different values with some overlap with the DIF list. Given the variation in these existing approaches, it seems reasonable to map the DIF and ECHO types into the ISO name element, which is free text, rather than into the function element which is a codeList.
  
=Online Resources=
+
==Online Resources==
  
Concept: URL
+
'''Concept''': URL <br>
Description: Address of the online resource
+
'''Description''': Address of the online resource
 
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Concept: Online Resource Description
+
'''Concept''': Online Resource Description <br>
Description: A brief description of the online resource
+
'''Description''': A brief description of the online resource
 
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</table>
  
Concept: Online Resource Function
+
'''Concept''': Online Resource Function <br>
Description: A description of the function of the online resource
+
'''Description''': A description of the function of the online resource
 
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Concept: Online Resource Name/Title
+
'''Concept''': Online Resource Name/Title <br>
Description: A name or title of the online resource
+
'''Description''': A name or title of the online resource
 
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Concept: Format of the Online Resource
+
'''Concept''': Format of the Online Resource <br>
Description: Identify the format of the online resource
+
'''Description''': Identify the format of the online resource
 
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Revision as of 16:18, August 8, 2012

As the World Wide Web has developed into a ubiquitous information source, links to on-line information and services have become critical elements in all metadata dialects. Some dialects emerged during the early days of the web when less was known about how it would develop and flourish. URLs were simple and self-explanatory and it was enough to include just the bare URL in the metadata. As URLs have increased in complexity, it has become more important to provide supporting information along with the links.

NASA GCMD Directory Interchange Format

URL's are described in DIF using the Related_URL field. They have the following properties:

<dif:Related_URL uuid="UUID">
    <dif:URL_Content_Type/>
    <dif:URL/>
    <dif:Description/>
</dif:Related_URL>

The URL_Content_Type field comes from the URL Content Type Keywords which provide standard names for a number of data systems and services. Data access URLs can be recognized by the URL_Content_Type = "GET DATA". The Related_URL field is highly recommended and may be repeated.

ECHO

The ECHO model includes several types of URLs, each with a unique set of properties:

<OnlineAccessURL>
    <URL/>
    <URLDescription/>
    <MimeType/>
</OnlineAccessURL>

<OnlineResource>
    <URL/>
    <Description/>
    <Type/>
    <MimeType/>
</OnlineResource>

<ProviderBrowseUrl>
    <URL/>
    <FileSize/>
    <Description/>
    <MimeType/>
</ProviderBrowseUrl>

ISO

The ISO Standards use CI_OnlineResources to describe links. They include the following properties:

<gmd:CI_OnlineResource>
    <gmd:linkage/>
    <gmd:protocol/>
    <gmd:applicationProfile/>
    <gmd:name/>
    <gmd:description/>
    <gmd:function/>
</gmd:CI_OnlineResource>

Connections

All of these approaches to describing online resources include properties that make links more self-explanatory and easier to use. There are some differences that need to be considered when comparing them:

  1. Types and Function Codes - All three dialects include a mechanism for classifying online resources. DIF and ISO use shared vocabularies and ECHO uses free text. The DIF vocabulary is hierarchical and includes roughly 35 choices. The ISO codeList includes 11 broad categories. The ECHO Collection metadata currently includes roughly 45 different values with some overlap with the DIF list. Given the variation in these existing approaches, it seems reasonable to map the DIF and ECHO types into the ISO name element, which is free text, rather than into the function element which is a codeList.

Online Resources

Concept: URL
Description: Address of the online resource

DIF ECHO ECS ISO netCDF(ncML) THREDDS Open Geospatial Consortium Sensor Observation Service (SOS) EML FGDC Dryad
/dif:DIF/dif:Related_URL/URL /echo:OnlineAccessURLs/echo:OnlineAccessURL/echo:URL //gmd:CI_OnlineResource/gmd:linkage/gmd:URL /eml:dataset/distribution/online/url/text /fgdc:metadata/idinfo/citation/citeinfo/onlink | /fgdc:metadata/idinfo/browse/browsen

Concept: Online Resource Description
Description: A brief description of the online resource

DIF ECHO ECS ISO netCDF(ncML) THREDDS Open Geospatial Consortium Sensor Observation Service (SOS) EML FGDC Dryad
/dif:DIF/dif:Related_URL/dif:Description /echo:OnlineAccessURLs/OnlineAccessURL/URLDescription //gmd:CI_OnlineResource/gmd:description/gco:CharacterString

Concept: Online Resource Function
Description: A description of the function of the online resource

DIF ECHO ECS ISO netCDF(ncML) THREDDS Open Geospatial Consortium Sensor Observation Service (SOS) EML FGDC Dryad
//gmd:CI_OnlineResource/gmd:description/gco:CharacterString

Concept: Online Resource Name/Title
Description: A name or title of the online resource

DIF ECHO ECS ISO netCDF(ncML) THREDDS Open Geospatial Consortium Sensor Observation Service (SOS) EML FGDC Dryad
/dif:DIF/dif:Related_URL/dif:URL_Content_Type/dif:Type > /dif:DIF/dif:Related_URL/dif:URL_Content_Type/dif:Subtype //gmd:CI_OnlineResource/gmd:name/gco:CharacterString

Concept: Format of the Online Resource
Description: Identify the format of the online resource

DIF ECHO ECS ISO netCDF(ncML) THREDDS Open Geospatial Consortium Sensor Observation Service (SOS) EML FGDC Dryad
echo:OnlineAccessURLs/echo:OnlineAccessURL/MimeType //gmd:CI_OnlineResource/gmd:applicationProfile/gco:CharacterString