Proposal number : Components and Composites

Date	2008/08/05
Contact(s)	Ted Habermann
Last edited	Timestamp
Status	draft
Assigned to release	to be determined
Resources	Some may be available

Overview

Large metadata repositories include significant amounts of information that is repeated in many metadata records. This includes on-line resources, contact information, citation information, instrument information, platform information, ... Our current system at NGDC allows us to store this sort of information once in a separate group of records, to edit this information once, and to include it as a “component” in a larger metadata record (a “composite”). Our repository currently hold thousands of components, some of which are included in hundreds of composites, so this capability is critical for us.

Our overall concept is that metadata “records” be viewed as collections of components that are held together by xlinks rather than as a single blob of XML in a database or a file. These xlinks would point to RESTful web services that would provide the component content in response to a URL. We hope that the MD_Identifiers that are included in numerous locations in the ISO 19115 and 19115-2 standards may provide a mechanism for linking these, although we would need to add new MD_Identifiers to these standards to make this work. For example, neither CI_OnlineResource or CI_ResponsibleParty packages currently include identifiers and both are clear candidates for componentization.

Proposal Type

• Type: GUI Change, Core Change, Module Change
• App: GeoNetwork
• Module: Not sure about this one yet

Links

• Documents:
• Email discussions:
• Other wiki discussions:

Voting History

Motivations

See Overview

Proposal

We propose to test this idea on a simple case that involves a CI_OnlineResource and a CI_ResponsibleParty, one of the simplest Component/Composite relationships in 19115. We will

• straightforward stuff
  • create a GeoNetwork Template that includes just an On_lineResource
  • add a MD_Identifier to that template
  • populate GeoNetwork database with some On_lineResources with identifiers
  • create a GeoNetwork Template that includes a ResponsibleParty and CI_Contact
• need some ideas stuff
  • figure out how to reference the On_lineResources using an xlink from the CI_Contact
  • figure out how to resolve the xlink so that we can index the On_lineResources.
  • search for a contact based on content of the On_lineResource

Backwards Compatibility Issues

This solution, as proposed, will only work in the context of ISO metadata standards

Risks

This solution, if it works, may suggest useful extensions to the ISO 19115 standard. That standard is up for review during 2008, so this might be a good time for such suggestions.

Participants

• Ted Habermann and his group at NOAA's National Geophysical Data Center