Coupled Resource ★★★★

When documenting a service, the nature of the relationship of the service to the data resources on which it interacts is important to capture so as to provide potential users an understanding of the applicability of such service to their needs. When a service is highly dependant on particular data, these data needs need to be documented in the service metadata.


Element Name	coupledResource
Parent	MD_Metadata.identificationInfo>SV_ServiceIdentification
Class/Type	SV_CoupledResources
Governance	Common ICSM
Purpose	Evaluation, Use
Audience	machine resource - ⭑ ⭑ ⭑
	general - ⭑ ⭑ ⭑
	resource manager - ⭑ ⭑ ⭑ ⭑
	specialist - ⭑ ⭑ ⭑
Metadata type	structural
ICSM Level of Agreement	⭑ ⭑

Definition

Further description of the data coupling in the case of tightly coupled services

ISO Requirements

There must be zero or many [0-*] coupledResource entries for the cited resource for a SV_ServiceIdentification package of class SV_CoupledResource in a metadata record. If a Coupling Type is tight, at least one instance of this element must be populated.

Discussion

The relation of a geospatial service to the data on which it operates is varied. This relation impacts the decisions one may make regarding the capture of useful metadata for such a service. These services fall into three categories depending on how tightly coupled the data is to the service: tightly, loosely, or mixed.

An example of a tightly coupled service would be a WFS service delivering a particular dataset. In the tightly coupled case, the service metadata shall describe both the service and the geographic dataset. The permitted values for the description of operations shall be constrained by the values defined by the datasets associated with the service.

An example of a loosely coupled service could be a reprojection service with user selected input datasets. Loosely coupled services may have an association with data types through the service type definition (SV_ServiceIdentification.serviceType). Dataset metadata need not be provided in the service metadata for the loosely coupled case.

A mixed coupling might be a WMS service into which you may add additional data sources of your choice. In a mixed coupling situation a single service instance may be associated to both kinds of data associated, loosely and tightly coupled.

Coupled resource information must be provided when the couplingType is tightly or mixed.

While there are numerous ways the related data resource may be captured in a service metadata record (e.g. operatesOn, operatedDataset, or even a sibling MD_DataIdentifcation package), ISO 19115-1 recommends coupledResource as minimum metadata required for the discovery of service resources.

Best Practice Recommendations

Therefore - the element coupledResource should be populated in all service metadata records where the Coupling Type is tight. One instance for each coupled resource should be populated. This should be done using the SV_CoupledResource.resourceReference citing the name and online location of the metadata for the coupled resources.

Recommended Sub-Elements

ICSM recommends population of SV_CoupledResources sub-elements as follows:

scopedName (type - scopedName) [0..1] Scoped identifier of the resource in the context of the given service instance. This ScopedName is the name of the resources as it is used by a service instance (e.g. feature type name in a WFS or layer name in a WMS).
resourceReference - (class - CI_Citation) [0..*] reference to the resource on which the service operates. Recommended CI_Citation elements to include:
- title - (type - charStr)*[1..1] Mandatory - the name by which the cited data resource is known as described in its metadata. May be different than the scoped name
- onlineResource - (class - CI_OnlineResource) [0..*] Highly Recommended. The online reference to the cited resource metadata (or landing page). Recommended CI_OnlineResource sub-elements include:
  - linkage - Mandatory for (class - CI_OnlineResource). A URL link to the metadata for the data resource.
  - description - E.g. “Metadata for dataset in OWL GeoNetwork Catalogue”

Also Consider

There are numerous alternate ways to document related dataset to a service. We recommend coupledDataset in line with ISO 19115-1 advice in section F.2 Metadata for the discovery of non-service geographic resources. Here we list some of the alternatives and why we do not recommnd them.

Coupling Type If not tight or mixed, CoupledResources need not be populated.
operatesOn - SV_ServiceIdentification.operatesOn - Not Recommended. This element is of class - MD_DataIdentification and thus creates a metadata record with multiple MD_Identifier elements. This creates confusion within a metadata record and upon harvesting to other metadata systems, thus should be avoided.
resource - SV_ServiceIdentification.coupledResource.resource - Not Recommended. This element is of class - MD_DataIdentification and thus creates a metadata record with multiple MD_Identifier elements. This creates confusion within a metadata record and upon harvesting to other metadata systems and thus should be avoided. Note - When resource is used, resourceReference cannot be used. When resourceReference is used, resource cannot be used.
operatedDataset - SV_ServiceIdentification.operatedDataset - As this is of class - CI_Citation, its use does not suffer the same issues as the above option. However, the lack of the ScopedName provided in the CoupledResource option means that one cannot include both the resource name and the name by which the service presents it.

Outstanding Issues

CORE ISSUE: Choice of Element to Hold Related Data Resource Reference
There are numerous ways the related data resource may be captured in a service metadata record (e.g. operatesOn, operatedDataset, or even a sibling MD_DataIdentification package. The choice of coupledResource is made for the following reasons. ISO 19115-1 recommends coupledResource as minimum metadata required for the discovery of service resources. The options operatesOn, SV_CoupledResource.resource and a sibling identificationInfo/MD_DataIdentification all require a MD_Identifier package. This would create metadata records that identify more than one resource. ICSM guidance is that such a situation be avoided as it could confuse other catalogues that expect a one-to-one relationship between metadata resources and resources.

Examples

GA

{example - if any useful}

ABARES

{example - if any useful}

Others

{### who - example - if any useful}}

XML -

<mdb:MD_Metadata>
....
  <mdb:identificationInfo>
     <srv:SV_ServiceIdentification>
        <mri:citation>
           <cit:CI_Citation>
           ....
           </cit:CI_Citation>
        </mri:citation>
        <mri:abstract/>
        <srv:serviceType>
           <gco:ScopedName>view</gco:ScopedName>
        </srv:serviceType>
        <srv:couplingType>
           <srv:SV_CouplingType codeList="http://standards.iso.org/iso/19115/resources/Codelists/cat/codelists.xml#SV_CouplingType"
                                codeListValue="tight"/>
        </srv:couplingType>
        <srv:coupledResource>
           <srv:SV_CoupledResource>
              <srv:scopedName>
                 <gco:ScopedName>MyLayerName</gco:ScopedName>
              </srv:scopedName>
              <srv:resourceReference>
                 <cit:CI_Citation>
                    <cit:title>
                       <gco:CharacterString>MyDataSet</gco:CharacterString>
                    </cit:title>
                    <cit:onlineResource>
                       <cit:CI_OnlineResource>
                          <cit:linkage>
                             <gco:CharacterString>https://dev.geodata.nz/geonetwork/srv/eng/catalog.search#/metadata/4c0a67e1-04ce-e2d8-57d8-33f8e063aaf0</gco:CharacterString>
                          </cit:linkage>
                          <cit:protocol gco:nilReason="missing">
                             <gco:CharacterString/>
                          </cit:protocol>
                          <cit:name gco:nilReason="missing">
                             <gco:CharacterString/>
                          </cit:name>
                          <cit:description>
                             <gco:CharacterString>Metadata for dataset in OWL GeoNetwork Catalogue</gco:CharacterString>
                          </cit:description>
                          <cit:function>
                             <cit:CI_OnLineFunctionCode codeList="http://standards.iso.org/iso/19115/resources/Codelists/cat/codelists.xml#CI_OnLineFunctionCode"
                                                        codeListValue=""/>
                          </cit:function>
                       </cit:CI_OnlineResource>
                    </cit:onlineResource>
                 </cit:CI_Citation>
              </srv:resourceReference>
           </srv:SV_CoupledResource>
        </srv:coupledResource>
        <srv:containsOperations>
        ....
        </srv:containsOperations>
     </srv:SV_ServiceIdentification>
  </mdb:identificationInfo>
....
</mdb:MD_Metadata>

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UML diagrams

Recommended elements highlighted in yellow

Coupled Resource

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