FGDC RSE to ISO Crosswalks: Data Quality

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The Data Quality approaches in both standards involve three major types of information: Reports, Sources, and Process Steps. These fundamental building blocks are compared in the tables below.


Contents

Reports

The FGDC quality section included four types of reports all as free text. ISO 19115 subdivided these four types into more detailed types and significantly increased the structure of the reports (see Report Structure).

FGDC ISO FGDC ISO
ReportCompletenessCompletenessComissionPositional AccuracyAbsoluteExternalPositionalAccuracy
CompletenessOmission RelativeInternalPositionalAccuracy
Logical ConsistencyConceptualConsistency GriddedDataPositionalAccuracy
DomainConsistencyAttribute AccuracyThematicClassificationCorrectness
FormatConsistency NonQuantitativeAttributeAccuracy
TopologicalConsistency QuantitativeAttributeAccuracy

In addition, ISO 19115 adds two new report types.

Report Type Sub-Type
Temporal AccuracyAccuracyOfATimeMeasurement
TemporalConsistency
TemporalValidity
Usability

Sources

The FGDC/RSE and ISO source descriptions are essentially identical at the highest level, however, at the detailed level the ISO standard includes some significant improvements. Several important improvements are associated with the ISO citation. First, in FGDC the citation is conceived as a reference to a scientific paper. It includes authors (called originators), but no contact information. This makes it difficult to describe unpublished data as sources. The ISO citation includes people in multiple roles (author, publisher, principle investigator, etc), and full contact information for all of those people. Second, in the FGDC case, the source is identified by an abbreviation that is unique only within the lineage section of a particular metadata record. This is similar to the model used for references in scientific papers where a single source could be referenced as Doe 2008 in one place and as Doe 2008b in another. The scope of an identifier is the reference list for that particular paper. In the ISO case, the source is identified by an MD_identifier that includes a namespace and an identifier defined to be unique in that namespace. This disambiguates references to sources across all metadata records.

A final benefit of the ISO Source is hidden in the extent object. This object allows the description of a spatial extent for a given source in addition to the time period which is included in the FGDC.

FGDC ISO
SourceCitationMD_Metadata.dataQualityInfo.DQ_DataQuality.lineage.LI_Lineage.source.LI_Source.sourceCitation
AbbreviationMD_Metadata.dataQualityInfo.DQ_DataQuality.lineage.LI_Lineage.source.LI_Source.sourceCitation.CI_Citation.identifier
ContributionMD_Metadata.dataQualityInfo.DQ_DataQuality.lineage.LI_Lineage.source.LI_Source.description
ScaleMD_Metadata.dataQualityInfo.DQ_DataQuality.lineage.LI_Lineage.source.LI_Source.scaleDenomination
MD_Metadata.dataQualityInfo.DQ_DataQuality.lineage.LI_Lineage.source.LI_Source.sourceReferenceSystem
Media
TimePeriodMD_Metadata.dataQualityInfo.DQ_DataQuality.lineage.LI_Lineage.source.LI_Source.sourceExtent.EX_Extent.temporalElement
Processing_LevelMD_Metadata.dataQualityInfo.DQ_DataQuality.lineage.LI_Lineage.source.LE_Source.processedLevel
MD_Metadata.dataQualityInfo.DQ_DataQuality.lineage.LI_Lineage.source.LE_Source.resolution

Process Steps

The process steps are also similar. The biggest difference being the addition of the rationale element to the ISO standard. Being able to describe why process steps were done is clearly useful in many cases.

FGDC ISO
Process StepDescriptionMD_Metadata.dataQualityInfo.DQ_DataQuality.lineage.LI_Lineage.processStep.LI_ProcessStep.description
TimeMD_Metadata.dataQualityInfo.DQ_DataQuality.lineage.LI_Lineage.processStep.LI_ProcessStep.dateTime
ContactMD_Metadata.dataQualityInfo.DQ_DataQuality.lineage.LI_Lineage.processStep.LI_ProcessStep.processor
MD_Metadata.dataQualityInfo.DQ_DataQuality.lineage.LI_Lineage.processStep.LI_ProcessStep.rationale
Source UsedMD_Metadata.dataQualityInfo.DQ_DataQuality.lineage.LI_Lineage.processStep.LI_ProcessStep.source
Source ProducedMD_Metadata.dataQualityInfo.DQ_DataQuality.lineage.LI_Lineage.processStep.LI_ProcessStep.output
ProcessingMD_Metadata.dataQualityInfo.DQ_DataQuality.lineage.LI_Lineage.processStep.LE_ProcessStep.processingInformation.LE_Processing
AlgorithmMD_Metadata.dataQualityInfo.DQ_DataQuality.lineage.LI_Lineage.processStep.LE_ProcessStep.processingInformation.LE_Processing.algorithm.LE_Algorithm

Process_Step.Process_Date

The RSE adds “Not Applicable” as a possible value for this date.

Algorithm and Processing Information

The FGDC RSE introduced a standard approach to describing algorithms and processing information. This is also available in ISO 19115.

Process_Step.Algorithm_Information

The RSE Algorithm_Information section is included as a part of the Process_Step. The section includes four elements that crosswalk directly into the ISO 19115-2 LE_Algorithm object which is repeatable and contains a citation and a description:

RSE ElementWhat is it?ISO
Algorithm_IdentifiersCitationMD_Metadata.dataQualityInfo.DQ_DataQuality.lineage.LI_Lineage.processStep.LE_ProcessStep.processingInformation.LE_Processing.algorithm.LE_Algorithm.citation.CI_Citation.identifier
Algorithm_Description [Description | Citation] MD_Metadata.dataQualityInfo.DQ_DataQuality.lineage.LI_Lineage.processStep.LE_ProcessStep.processingInformation.LE_Processing.algorithm.LE_Algorithm.citation / description
(1{Algorithm_Change_History}n)List of Process_StepsMD_Metadata.dataQualityInfo.DQ_DataQuality.lineage.LI_Lineage.processStep
(1{Algorithm_Peer_Review_Information}n) List of Process_StepsMD_Metadata.dataQualityInfo.DQ_DataQuality.lineage.LI_Lineage.processStep

Algorithm Change History

The FGDC Remote Sensing Extensions include a description of the history of changes to the algorithm used to produce a product. This structure is:

Data_Quality_Information
  Lineage
    Process_Step
      Algorithm_Information
        1{Algorithm_Change_History}n
          [Algorithm_Change_Description | Algorithm_Change_Reference]

The Algorithm section of a Process_Step can contain any number of Algorithm_Change_History sections, each of which can contain an Algorithm_Change_Description (a ProcessStep) or an Algorithm_Change_Reference (a Citation).

In the ISO 19115-2 case the structure is:

DQ_Data_Quality
  Lineage
    LE_ProcessStep
      LE_Processing
        LE_Algorithm

Times occur in this structure twice: as a time range in the DQ_DataQuality.scope.extent and as a single dataTime in the ProcessStep. This seems to offer two approaches to describing changes in algorithms: as a series of processSteps that describe each change or as a series of DQ_DataQuality objects that describe time periods (and spatial extents) of constant algorithm. In this case the DQ_Scope.level could be “software”, although this is not strictly equivalent to algorithm. Do we need to add a scopeCode of algorithm?

Processing_Information

The RSE Processing_Information section is used to describe details of the processing that is associated with a process step. It includes seven elements:

RSE ElementWhat is it? ISO
Processing_IdentifiersCitationMD_Metadata.dataQualityInfo.DQ_DataQuality.lineage.LI_Lineage.processStep.LE_ProcessStep.processingInformation.LE_Processing.softwareReference/documentation (both citations)
1{Processing_Input_Dataset}nIdentifier + [Description | Citation] MD_Metadata.dataQualityInfo.DQ_DataQuality.lineage.LI_Lineage.processStep.LI_ProcessStep.source.LI_Source.sourceCitation.CI_Citation.identifier + metadata.dataQualityInfo.lineage.processStep.source.sourceCitation
(1{Ancillary_Dataset}n) Identifier + [Description | Citation] + Command_LineMD_Metadata.dataQualityInfo.DQ_DataQuality.lineage.LI_Lineage.processStep.LI_ProcessStep.source.LI_Source.sourceCitation.CI_Citation.identifier + MD_Metadata.dataQualityInfo.DQ_DataQuality.lineage.LI_Lineage.processStep.LI_ProcessStep.source.LI_Source.sourceCitation + MD_Metadata.dataQualityInfo.DQ_DataQuality.lineage.LI_Lineage.processStep.LE_ProcessStep.processingInformation.LE_Processing.ProcessingInformation.runTimeParameters
Processing_SoftwareDescription | CitationMD_Metadata.dataQualityInfo.DQ_DataQuality.lineage.LI_Lineage.processStep.LE_ProcessStep.processingInformation.LE_Processing.softwareReference/documentation (both citations)
Processing_ProcedureRun History (Process Steps)+ Environment + (Description) MD_Metadata.dataQualityInfo.DQ_DataQuality.lineage.LI_Lineage.processStep + MD_Metadata.dataQualityInfo.DQ_DataQuality.lineage.LI_Lineage.processStep.LE_ProcessStep.processingInformation.LE_Processing.proceedureDescription
0{Processing_Change_History}1List of process_stepsMD_Metadata.dataQualityInfo.DQ_DataQuality.lineage.LI_Lineage.processStep
(1{Processing_Documentation}n)CitationMD_Metadata.dataQualityInfo.DQ_DataQuality.lineage.LI_Lineage.processStep.LE_ProcessStep.processingInformation.LE_Processing.softwareReference/documentation (both citations)
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