The role of registries within a spatial data infrastructure

Simon Cox Rob Atkinson

Research Scientist Spatial Architect

16 April 2008

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Outline

• Spatial Data Infrastructure ~ Cyberinfrastructure

• Brief comment on state of SDI deployment• Analysis examples

• Metadata

• Concept identifiers

• Expanded role for registries

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SDIs

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Spatial Data Infrastructure ideal

• Goal: automated workflow/service-chain composition on-demand

matching clients to services

• Matching services and clients requires components to be described to a high level of detail

• service type• content that it exposes

• Schema• vocabularies

• queries that it supports• response formats• quality of service• …

“Service classification axes”

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SDI reality

• Some service instances• OGC-WFS, WMS, WCS, OpenDAP

• Dataset metadata directories• Clearinghouses, GEON, ESIP, ASDD, Go-Geo …

• Is this enough to achieve the goal? • No

• Is the number of registered resources growing? • Not enough

• Are the right resources being registered?• No

• Why not?• Governance patterns not resolved• Metadata is insufficient, but creating it is too hard• Semantic interoperability requires community agreements

• See Markup/Standards-based methodology paper

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Metadata

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Metadata capture

• Everyone agrees that metadata is a good idea • But researchers are reluctant to provide it

Why?

• Not integrated with workflow• No perceived reward

• Researchers don’t themselves rely on metadata-based discovery systems

• Tedious to create• …

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Is it the metadata models?

• Standards are complex• … but they are also highly normalized

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It’s the implementation!

• Records are usually de-normalized

• A better way

• Records refer to externally governed elements

 <gmd:contact>      <gmd:CI_ResponsibleParty>         <gmd:organisationName>            <gco:CharacterString>Geoscience Australia (GA)</gco:CharacterString>         </gmd:organisationName>         <gmd:positionName>            <gco:CharacterString>Director, Sales and Distribution, CIMA</gco:CharacterString>         </gmd:positionName>         <gmd:contactInfo>            <gmd:CI_Contact>               <gmd:phone>                  <gmd:CI_Telephone>                     <gmd:voice>                        <gco:CharacterString>+61 2 6249 9966</gco:CharacterString>                     </gmd:voice>                     <gmd:facsimile>                        <gco:CharacterString>+61 2 6249 9960</gco:CharacterString>                     </gmd:facsimile>                  </gmd:CI_Telephone>               </gmd:phone>               <gmd:address>                  <gmd:CI_Address>                     <gmd:deliveryPoint>                        <gco:CharacterString>GPO Box 378 </gco:CharacterString>                     </gmd:deliveryPoint>                     <gmd:city>                        <gco:CharacterString>Canberra</gco:CharacterString>                     </gmd:city>                     <gmd:administrativeArea>                        <gco:CharacterString>ACT</gco:CharacterString>                     </gmd:administrativeArea>                     <gmd:postalCode>                        <gco:CharacterString>2601</gco:CharacterString>                     </gmd:postalCode>                     <gmd:country>                        <gco:CharacterString>Australia</gco:CharacterString>                     </gmd:country>                     <gmd:electronicMailAddress>                        <gco:CharacterString>sales@ga.gov.au</gco:CharacterString>                     </gmd:electronicMailAddress>                  </gmd:CI_Address>               </gmd:address>            </gmd:CI_Contact>         </gmd:contactInfo>         <gmd:role>            <gmd:CI_RoleCode codeList="http://www.isotc211.org/2005/resources/Codelist/gmxCodelists.xml#CI_RoleCode"                             codeListValue="custodian">custodian</gmd:CI_RoleCode>         </gmd:role>      </gmd:CI_ResponsibleParty>   </gmd:contact>

 <gmd:contact xlink:href=“urn:cgi:party:CGI:GA”/>

• Each record reproduces every elementEach repository assumes governance of all the elements

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Normalized records distributed governance

• Metadata records should primarily consist of a set of references - Use keyboard only for title/label & abstract/description!

- Drop-down lists for everything else- List == (online) register

Separate registers for key classes, e.g.• Responsible party

• Access conditions

• Feature types …

• These registers are under independent governance• Access Federation data

• standard licenses

• published community schemas

Infrastructure

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Identifiers

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CGI persistent identifiers

• IUGS Commission for Geoscience Information

• GeoSciML Testbed III• Interoperable WFS from 10 geological surveys

• USGS, GSC, BGS, BGR, GA, GSV, SGU, APAT, GSJ, AzGS

• More logos here

• Interoperability levels:• Schematic/model – common XML Schema

• GeoScML v2.0 - see other paper in this conference

• Semantic – common vocabularies

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GeoSciML Example

<MappedFeature>    …     <observationMethod> <CGI_TermValue>

            <value codeSpace="urn:cgi:classifierScheme:GA:1MillionGeology_ObservationMethods“ >GSNSW785</value>

        </CGI_TermValue></observationMethod>    <positionalAccuracy> <CGI_NumericValue>

            <principalValue uom="urn:ogc:def:uom:UCUM:m">500</principalValue>        </CGI_NumericValue> </positionalAccuracy>    <samplingFrame

xlink:href="urn:cgi:classsifier:GA:SurfaceGeologyOfEasternAustralia_1MillionScale"/>     <specification>

        <LithologicUnit >            <gml:description>Mafic volcaniclastic sandstone, siltstone, shale, chert; minor limestone, conglomerate</gml:description>             <gml:name codeSpace="urn:cgi:classifierScheme:GA:StratigraphicLexicon:Unitname“

>Kabadah Formation</gml:name>             <gml:name codeSpace="urn:cgi:classifierScheme:GA:StratigraphicLexicon:Map_symbol“

>Ojck</gml:name>             <gml:name codeSpace="urn:ietf:rfc:2141">urn:cgi:feature:GA:Stratno:29570</gml:name>

            <observationMethod> <CGI_TermValue>                    <value codeSpace="urn:cgi:classifierScheme:GA:ObservationMethods“

>published description</value>                </CGI_TermValue> </observationMethod>

            <purpose>typicalNorm</purpose>             <preferredAge> <GeologicEvent>

<eventAge> <CGI_TermValue>                            <value codeSpace="urn:cgi:classifierScheme:ICS:StratChart:2004“

>urn:cgi:classifier:ICS:StratChart:2004:Ordovician</value>                        </CGI_TermValue> </eventAge>

 <eventProcess> <CGI_TermValue>                            <value codeSpace="urn:cgi:classifierScheme:GA:Process">unspecified</value>                        </CGI_TermValue> </eventProcess>

 </GeologicEvent> </preferredAge> …

Most property values are references to registersCommon values interoperability

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Concept identifiers

• Concepts are denoted by language-neutral identifiers

• Identifiers must be universal and persistent• urn:ogc:def:crs:EPSG:6.14:4326

• urn:cgi:classifier:ICS:StratChart:2008:ediacaran

• urn:cgi:classifierscheme:ICS:StratChart:2008

• urn:cgi:schema:CGI:GeoSciML:2.0

• urn:cgi:featuretype:CGI:GeoSciML:2.0:GeologicUnit

• urn:cgi:feature:USGS_NGDM:Id56jn23

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“Controlled vocabularies”

• Concepts exist in context• urn:ogc:def:crs:EPSG:6.14:4326

• urn:cgi:classifier:ICS:StratChart:2008:ediacaran

• urn:cgi:classifierscheme:ICS:StratChart:2008

• urn:cgi:schema:CGI:GeoSciML:2.0

• urn:cgi:featuretype:CGI:GeoSciML:2.0:GeologicUnit

• urn:cgi:feature:USGS_NGDM:Id56jn23

• Term from versioned vocabulary owned by an organization• Feature type defined in a schema owned by an organization

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Governance

• The governance arrangements require separate registers of: • Classifiers, classifier-schemes

• Resource classes – def, classifier, schema, featuretype, feature,

• Concept owners – EPSG, ICS, CGI, USGS_NGDM

• and are reflected in/enforced by the structure of the persistent identifier

• urn:ogc:def:crs:EPSG:6.14:4326

• urn:cgi:classifier:ICS:StratChart:2008:ediacaran

• urn:cgi:classifierscheme:ICS:StratChart:2008

• urn:cgi:schema:CGI:GeoSciML:2.0

• urn:cgi:featuretype:CGI:GeoSciML:2.0:GeologicUnit

• urn:cgi:feature:USGS_NGDM:Id56jn23

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Structured vs. opaque identifiers?

• URN vs DOI?

• Use structured identifiers for strongly governed concepts, system resources

• Slow rate of change, many references,

• Identifiers must be stable

• Resolution often not needed

• Useful if they are memorable

• Use opaque identifiers for weakly governed data resources• Frequent update, few references

• Data & identifiers may be transient

• Should be easily resolvable

• Don’t need to be memorable

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Summary

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Key points

• Many controlled vocabs + other lists required for an infrastructure

• Each is typically under independent governance

Almost all “lists” (and ontologies) should be managed as “registers”

• Semantic web (AI for C21?) hopes to do this automatically?

• Agreements (standards) are possible in the context of coherent technical communities

• To enable an infrastructure, we need a lot of registers • These must

• Use persistent identifiers for both registers and contents

• Be resolvable

• Have transparent governance arrangements

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ISO 19135 Register Organization model

Contact UsPhone: 1300 363 400 or +61 3 9545 2176

Email: enquiries@csiro.au Web: www.csiro.au

Thank you

Exploration & MiningSimon CoxResearch Scientist

Phone: 08 6436 8639Email: Simon.Cox@csiro.auWeb: www.seegrid.csiro.au

Land & WaterRob AtkinsonSpatial Architect

Phone: 02 4226 4339Email: Rob.Atkinson@csiro.au