ISO Citations

From NOAA Environmental Data Management Wiki

Citations are used to provide information about citing the resource being described in the metadata or to refer to resources outside of the metadata record.


CI_Citation Object
The CI_Citation includes two required and eleven optional elements and introduces several new objects. The CI_Series object gives the name, issue, and page numbers of an article in a periodical. The ISBN and ISSN elements are internationally recognized identifiers for books and periodicals. The MI_Identifier and CI_Date objects are discussed below.


CI_Citation serves two purposes in the ISO 19115 Standard. First, it gives the information required to cite the data or the service (the resource) that is being described in the metadata. This CI_Citation can be part of the gmd:MD_DataIdentification or srv:ServiceIdentification objects.

Usage Description and Xpath

Resource Citation

WhereAreCI Citations.MD Identification.png

The Resource Citation includes information that should be used when citing the resource that is being described by the metadata record. It includes descriptions of the people involved in the creation of the resource. They usually have roles of originator, author, or principleInvestigator.





Citation Locations
Second, CI_Citations provide information about external references that are related to the resource being described and provide additional documentation. This Figure shows most of the places where CI_Citations occur. Those shown in red were added in ISO 19115-1. In many of these situations the CI_Citation is in an object with a generally small amount of additional annotation information. This additional information is available to the user so they may not need to look up the resource cited in the CI_Citation. These objects are termed CI_Citation++.

The most straightforward member of this group is the MI_Identifier, which includes a code, the identifier, and a CI_Citation for the authority for the code. The MD_Identifier is used throughout the standard to attach a unique identifier to objects, including CI_Citations.

Usage Description and Xpath


WhereAreCI Citations.MD Identifier.png
CI_Citation + code = MD_Identifier

The MD_Identifier is the simplest of the CI_Citation++ objects. It includes a code and an authority. The code is an alphanumeric value identifying an object in a namespace that is maintained by the authority. In this case the CI_Citation cites the authority for the code. In many ways this is similar to the namespace for the code. It is the authority which understands and can explain or resolve the code. There is no agreed upon approach for how the namespace is described in the CI_Citation.


ReferenceSystem Identifier

WhereAreCI Citations.RS Identifier.png
CI_Citation + code + codeSpace + version = RS_Identifier

The RS_Identifier extends the MD_Identifier by adding a codeSpace and a version for the namespace. These additions address the lack of an ageed upon approach for describing a namespace using the authority/gco:CI_Citation alone. However, the standard only supports RS_Identifiers in the referenceSystemInfo class.


Keyword Thesaurus Citation

WhereAreCI Citations.MD Keywords.png
CI_Citation + keyword + type = MD_Keywords

The MD_Keywords object is similar to an MD_Identifier in that it gives a keyword that is unique in a "namespace" that is maintained by the individual or organization cited in the thesaurusName. In this case, the type codeList is used to group related keywords.

/gmi:MI_Metadata/gmd:identificationInfo/gmd:MD_DataIdentification | srv:ServiceIdentification/gmd:descriptiveKeywords/gmd:MD_Keywords/gmd:thesaurusName

Algorithm Citation

WhereAreCI Citations.LE Algorithm.png
CI_Citation + description = LE_Algorithm

The Algorithm Citation is straightforward. It includes a description that, like the description in the CI_OnlineResource object, should provide information that identifies the algorithm used to process data so that a user can understand that information without following the citation. The description is similar to an abstract for the algorithm referenced in the CI_Citation.


Conformance Standard Specification Citation

WhereAreCI Citations.DQ ConformanceResult.png
CI_Citation + explanation + pass = DQ_ConformanceResult

The DQ_ConformanceResult is a good example of including critical information in the standard while referencing an external resource for more information. In this case the critical information is a brief explanation of the conformance test and the result of the test. If a user needs more information about the specifics of the test, they can follow the citation to the specification.


Source Citation

WhereAreCI Citations.LE Source.png

CI_Citation + description + scaleDenominator + sourceReferenceSystem + sourceExtent + processedLevel + resolution + sourceStep = LE_Source

/gmi:MI_Metadata/gmd:dataQualityInfo/gmd:MD_DataQuality/gmd:lineage/gmd:LE_Lineage/gmd:source | gmd:output/gmd:LE_Source/gmd:sourceCitation

Data Quality Evaluation Procedure Citation

WhereAreCI Citations.DQ Element.png

Feature Catalog Citation

WhereAreCI Citations.MD FeatureCatalogDescription.png

Application Schema Citation

WhereAreCI Citations.MD ApplicationSchemaInformation.png

CI_Citation + schemaLanguage + constraintLanguage + schemaAscii + graphicsFile + softwareDevelopmentFile + softwareDevelopmentFIleFormat = MD_ApplicationSchemaInformation



CodeLists as Types

As described earlier, codeLists provide shared vocabularies throughout the ISO Standard. The fact that these vocabularies are shared makes it possible to use them as well known tags for content in the standard. An excellent example of this occurs in the CI_Date object that gives dates for CI_Citations. That object includes a date string and the CI_DateTypeCode codeList that can be either creation, publication, or revision. This single date, along with the codeList, covers three common types of dates that are required in citations. Contrast this with the editionDate attribute that is a single date the purpose of which is expressed in the name of the attribute rather than with a tag.

Extensions and Revisions

The CI_Citation object used in the ISO Standards originated in the world of physical objects: books and scientific papers that need to be referenced from metadata records. This approach works well for many items, but not for the increasing number of digital resources that are available online. These important resources can only be associated with a CI_Citation using a rather circuitous path: //gmd:CI_Citation/gmd:citedResponsibleParty/gmd:CI_ResponsibleParty/gmd:contactInfo/gmd:CI_Contact/gmd:onlineResource and it is not at all clear that a URL in the contact information for the citedResponsibleParty is actually the URL for the resource being cited. In short, the CI_Citation does not work well for citations to online resources.

This shortcoming can be addressed by adding a CI_OnlineResource to the CI_Citation. Of course, this would be an extension to the original standard and could result in in-compatibilities or unexpected results. The Standard recognizes the need for extensions and provides an object for describing them. There is also a revision process for ISO Standards that can be invoked every five years by any member of ISO. This process is currently underway for ISO 19115 and adding a CI_OnlineResource to the CI_Citation is one of the proposed revisions. Different groups make different decisions about when to adopt a new version of the standard. For changes that most users agree on, like the one discussed here, most groups wait until the standard is at the Committee Draft stage. Very few technical changes are expected after that so the risks of adoption are relatively small.