Most large organisations that distribute spatial data, catalogue the existence of that data using a metadata catalogue system such as GeoNetwork opensource (geonetwork-opensource.org). AusSeabed Contributing Hubs must provide a catalogue that can be harvested by AODN (and others). The preferred mechanism employed is an Open Geospatial Consortium (OGC) compliant Catalogue Service for the Web (CSW). AusSeabed requires that metadata entries be systematised to support downstream searching and filtering.
There are several metadata standards for describing spatial data, but ISO19115 continues to grow in popularity. The standard itself provides a wide range of flexibility in the forms of XML that it accepts. It is rarely possible for a system to understand the semantics of every component of XML that meets the standard. Likewise, the standard permits different ways of representing the same information. What has emerged are profiles of the ISO19115 that have agreed meaning among subsets of the spatial community.
Key metadata fields compiled from above must be able be published using ISO19115-3 metadata through a catalogue service for the web - nominally GeoNetwork. GeoNetwork implements the following protocols to assist in the function of publishing and ingesting metadata:
OGC CSW
OAI-PMH
OpenSearch
Z39.50
and also provides its own API to interact with other systems and a DCAT/RDF search service.
GeoNetwork provides at least three method of editing metadata: a) a simple interface; b) the full interface; and c) an XML editor. Most metadata can be entered in the simple interface; however, a number of fields require the full editing interface or XML editor (or import) including:
Attribute | Location in XML |
Abstract | IdentificationInfo/Abstract |
Title | IdentificationInfo/Citation/Title |
Keywords | 1<mri:descriptiveKeywords> 2 <mri:MD_Keywords> 3 <mri:keyword> 4 <gco:CharacterString>marine</gco:CharacterString> 5 </mri:keyword> 6 <mri:type> 7 <mri:MD_KeywordTypeCode codeList="codeListLocation#MD_KeywordTypeCode" codeListValue="theme"/> 8 </mri:type> 9 </mri:MD_Keywords> 10</mri:descriptiveKeywords> |
Start Date | IdentificationInfo/Extent/TemporalExtent/TimePeriod/BeginPosition |
End Date | IdentificationInfo/Extent/TemporalExtent/TimePeriod/EndPosition |
Vessel (for surveys, not compilations) | Acquisition Information/Platform/Identifier |
Instrument (for surveys, not compilations) | Acquisition Information/Platform/Instrument/Identifier |
Vessel and instrument should also link to a valid vocabulary entry in a vocabulary server. e.g.
1<mcc:code> 2<gcx:Anchor xlink:href="'http://vocab.nerc.ac.uk/collection/C17/current/09SS' ">Southern Surveyor</gcx:Anchor> 3</mcc:code> |
Likewise, start and end ports should link to a valid vocabulary entry.
e.g. SeaDataNet Ports:
'http://vocab.nerc.ac.uk/collection/C38/current/BSH244/'
If as a Contributing Hub you have employed alternate technologies as long as the metadata can be harvested via an API like OGC CSW.
A fully marked up ISO-19115 XML example can be found here.
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