the role of registries within a spatial data infrastructure simon coxrob atkinson research...
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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
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