Network Working Group                                             S. Cox
Request for Comments: 5138                                         CSIRO
Category: Informational                                    February 2008


     A Uniform Resource Name (URN) Namespace for the Commission
  for the Management and Application of Geoscience Information (CGI)

Status of This Memo

  This memo provides information for the Internet community.  It does
  not specify an Internet standard of any kind.  Distribution of this
  memo is unlimited.

Abstract

  This document describes a URN (Uniform Resource Name) namespace that
  is engineered by the Commission for the Management and Application of
  Geoscience Information (CGI) for naming (i) persistent resources
  published by the CGI and (ii) resources published by organizations
  that wish them to be used in the context of services conforming to
  protocols and agreements issued by CGI.  The formal Namespace
  Identifier (NID) is "cgi".

1.  Introduction

  CGI is a Commission of the International Union of Geological Sciences
  (IUGS) concerned with developing best practices in the management and
  application of geoscience information.  The active membership is
  primarily drawn from organizations with statutory responsibility for
  providing geoscience information to external users (e.g., Geologic
  Surveys).  An important focus of activity is the development of
  standards for networked data interchange to complement or supersede
  the traditional map product.

  A number of documents, definitions, and other artifacts, are required
  to support this.  CGI wishes to provide persistent,
  location-independent identifiers for these resources.  In addition,
  organizations that subscribe to the interchange standards proposed by
  CGI require external identifiers for data objects that are
  transferred.  CGI wishes to provide a scheme to enable data providers
  to uniquely identify data, which is consistent with the requirements
  of the interchange framework.

  Products and services that conform to CGI endorsed interchange
  specifications enable users to exchange and process geoscience
  information across networks, computing platforms, and products.
  Interoperability in such an environment is facilitated by the use of



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  a system of identifiers that is global in scope.  CGI is the lead
  forum for statutory organizations that act as primary providers of
  technical data in this application domain.

  Motivated by these concerns, CGI would like to assign formal URNs to
  published resources in order to provide persistent,
  location-independent identifiers for them.  The process for
  registering a namespace identifier is documented in [RFC3406].

  The official IANA registry of URN namespaces is available online at:

  <http://www.iana.org/assignments/urn-namespaces>

2.  URN Specification for the "cgi" NID

  Namespace ID:

     cgi

  Registration Information:

     Registration Version Number: 1
     Registration Date: 2007-10-04

  Declared registrant of the namespace:

     Commission for Geoscience Information (Secretariat)
     c/o British Geological Survey
     Kingsley Dunham Centre
     Keyworth
     Nottingham
     Nottinghamshire
     NG12 5GG
     U K
     Attn. Ian Jackson ([email protected])

  Declaration of syntactic structure:

     The Namespace Specific String (NSS) of all URNs that use the "cgi"
     NID has the following structure:

     urn:cgi:{CGIResource}:{ResourceSpecificString}

     where the "CGIResource" is a US-ASCII string that conforms to the
     URN syntax requirements [RFC2141] and defines a specific class of
     resource type.  Each resource type has a specific labeling scheme
     that is covered by "ResourceSpecificString", which also conforms
     to the naming requirements of [RFC2141].



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     The CGI maintains a naming authority, the CGI Naming Authority
     (CGINA), that manages the assignment of CGIResource classes and
     the specific registration values assigned for each resource class.

  Relevant ancillary documentation:

     The CGI Naming Authority (CGINA) provides information on the
     registered resources and the registrations for each.  More
     information about CGINA and the registration activities and
     procedures to be followed are available at:

     <http://www.cgi-iugs.org/CGIIdentifierScheme>

     A URN resolver is available at:

     <http://www.cgi-iugs.org/uri>

     The resolver provides a registry of CGI URNs used in CGI services.

  Identifier uniqueness considerations:

     The CGINA manages resources using the "cgi" NID and is the
     authority for managing the resources and subsequent strings
     associated.  In the associated procedures, CGINA ensures the
     uniqueness of the strings themselves or permits secondary
     responsibility for management of well-defined sub-trees.

     CGI may permit use of experimental-type values that will not be
     registered.  As a consequence, multiple users may end up using the
     same value for separate uses.  As experimental usage is only
     intended for testing purposes, this should not interfere with
     operational services.

  Identifier persistence considerations:

     CGINA provides clear documentation of the registered uses of the
     "cgi" NID.  This is structured such that each CGIResource has a
     separate description and associated ResourceSpecificString with
     separate registration tables for elements of the strings that are
     separately maintained.

     The registration tables and information are published and
     maintained by CGINA on the CGI web site, indicated above.








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  Process of identifier assignment:

     CGINA defines CGIResource classes used with the "cgi" NID, and
     specifies the process for identifier assignment for each class.
     These are described at:

     <http://www.cgi-iugs.org/CGIIdentifierScheme>

     and a set of registers is linked from there.  Each such resource
     may have three types of registration activities:

        1) Registered values associated with CGI resources
        2) Registration of values or sub-trees to other entities
        3) Name models for use in experimental purposes

  Process for Identifier Resolution:

     The namespace is not listed with a Resolution Discovery System
     (RDS); this is not relevant.

  Rules for Lexical Equivalence:

     No special considerations; the rules for lexical equivalence of
     [RFC2141] apply.

  Conformance with URN Syntax:

     No special considerations.

  Validation mechanism:

     None specified.  URN assignment will be handled by procedures
     implemented in support of CGINA activities.

  Scope:

     Global

3.  Examples

  The following examples are representative URNs that have been
  assigned by CGINA:

  urn:cgi:document:CGI:CGIIdentifierScheme

     - identifies the document that describes the CGI Identifier
       Scheme.




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  urn:cgi:register:CGI:CGIResourceClasses

     - identifies the register of resource classes for which
       identifiers from the CGI scheme may be provided.

  urn:cgi:xmlns:CGI:GeoSciML:2.0

     - is the XML namespace for version 2.0 of GeoSciML, which is owned
       by CGI.

  urn:cgi:schema:GGIC:MineralOccurences:1.0:XMI

     - identifies the XML Metadata Interchange (XMI) representation of
       version 1.0 of the Mineral Occurrences information model owned
       by the (Australasian) Government Geoscience Information
       Committee.

  urn:cgi:featureType:CGI:GeoSciML:2.0:Fault

     - identifies the Fault feature-type from version 2.0 of the
       GeoSciML schema that is owned by CGI.

  urn:ogc:serviceType:CGI:GSML-FS:1.0

     - identifies version 1.0 of the "GSML-FS" service-type owned by
       CGI.

  urn:cgi:classifierScheme:ICS:StratChart:2004

     - identifies the 2004 edition of the Stratigraphic Chart published
       by the International Commission for Stratigraphy.

  urn:cgi:classifier:ICS:StratChart:2004:Silurian

     - identifies the geologic period designated Silurian from the 2004
       edition of the Stratigraphic Chart published by the
       International Commission for Stratigraphy.

  urn:cgi:classifier:GSV:Lithology:UIUYG1245NN07

     - identifies the concept given the designation UIUYG1245NN07 from
       the lithology scheme published by Geoscience Victoria
       (Australia).








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  urn:cgi:feature:USGS:2feb49bc-6755-11dc-8314-0800200c9a66

     - identifies a feature instance given the designation
       2feb49bc-6755-11dc-8314-0800200c9a66 by the US Geological
       Survey.

  urn:cgi:object:SGU:552cb080-6755-11dc-8314-0800200c9a66

     - identifies an object given the designation
       552cb080-6755-11dc-8314-0800200c9a66 by the Geological Survey of
       Sweden.

4.  Namespace Considerations

  There is currently no available namespace that will allow the CGI to
  uniquely specify and access resources, such as schemas and
  registries, that are required by organizations implementing CGI
  standards.  There is also a need for other standards organizations,
  such as the Open Geospatial Consortium (OGC) to be able to access
  CGI-specific resources.

  The CGI members considered use of other existing NIDs, such as those
  for OGC.  However, these do not support the semantics required and in
  particular do not allow for the delegation of identifier assignment
  within the CGI community that is demonstrated here.

5.  Community Considerations

  CGI standards require access to resources, such as schemas,
  registries, catalogues, documents, and services.  In order for the
  larger IT community to be able to implement applications that access
  CGI resources effectively, a unique namespace is required.  We desire
  these resources to be freely and openly available as a set of
  community resources.

  The design of the CGI namespace builds on the experience of the Open
  Geospatial Consortium (OGC) which has defined the framework of
  geospatial services within which CGI standards have been developed.
  The OGC membership has expertise in using the OGC URN [OGC-URN]
  [OGC-DEF], gained through implementation experiments and a variety of
  operational testbeds.  The CGI namespace is compatible with this
  experience.

6.  Security Considerations

  There are no additional security considerations other than those
  normally associated with the use and resolution of URNs in general.




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7.  IANA Considerations

  This document defines a URN NID registration of "cgi", which has been
  entered into the IANA registry located at:

  <http://www.iana.org/assignments/urn-namespaces>

8.  References

8.1 Normative References

  [RFC2141] Moats, R., "URN Syntax", RFC 2141, May 1997.

  [RFC3406] Daigle, L., van Gulik, D., Iannella, R., and P. Faltstrom,
            "Uniform Resource Names (URN) Namespace Definition
            Mechanisms", BCP 66, RFC 3406, October 2002.

8.2 Informative References

  [OGC-URN] Reed, C., "A URN namespace for the Open Geospatial
            Consortium (OGC)", Work in Progress, October 2007.

  [OGC-DEF] Whiteside, A., "Definition identifier URNs in OGC
            namespace", OpenGIS Best Practice document, OGC 06-023r1,
            August 2006.  Available [online]:
            <http://portal.opengeospatial.org/files/?artifact_id=16339>

9.  Acknowledgement

  Thanks to Carl Reed for preparing the document, "A URN Namespace for
  the Open Geospatial Consortium", upon which this submission is based.

Author's Address

  S.J.D. Cox
  Commonwealth Scientific and Industrial Research Organisation
  PO Box 1130
  Bentley, WA, 6102, Australia
  EMail: [email protected]












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