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Registry Working Group Work Package 3: Metadata Specifications

Progress Report: 01 July 2003

RayPlante, Work Package Lead


1. Draft Metadata Schema

In keeping with the modeling process proposed by the Data Modeling Working Group, development of the resource metadata has followed in two parts: first, a prose document describing the model and metadata concepts, and second, an rendering of that document in XML Schema. The prose document is currently in the form of "Resource and Service Metadata" (soon to be renamed to simply "Resource Metadata").

1.1. Resource Metadata document

The "Resource and Service Metadata" (RSM) version 0.6 was presented at the IVOA Interoperability Meeting in Baltimore in October 2002. Version 0.7 was prepared for the Interoperability meeting in Cambridge in May 2003. This version updated the overall architecture to allow anything that is describably and identifiable to be a resource. It added a number of terms for describing education and outreach resources. It also expanded the description of services. Finally, it included minor adjustments addressing feedback from the first NVO registry prototyping.

Version 0.8 (to be renamed "Resource Metadata") is being prepared for release in early July 2003. It will incorporate address the simpler suggestions that have come out of the AstroGrid and NVO registry prototyping efforts and from the Registry Working Group in general.

Some of the feedback on the RSM document touched on fundemental issues of the metadata model that could not be easily resolved in a short time. To address these concerns, we are currently conducting a more comprehensive review of the resource metadata model. This review is may result in major changes to model which are expected to be incorporated into Version 0.9. We have set a goal of reaching consensus on these changes by the end of July 2003.

1.2. XML Schema Modeling

Renderings of the resource metadata schema using XML Schema began after the release of RSM V0.6. The AstroGrid project produced an XML Schema based on the RSM for use in their first prototype registry, capturing the major components of the metadata into separate Schema files. NVO developed a similar schema, VOResource, for their prototype registry. Use of this schema demonstrated how metadata from different namespaces could be used together in a single XMl document. The prototype also demostrated the use of VOResource within the Open Archives Initiative (OAI) Protocol for Metadata Harvesting.

At the IVOA Interoperability meeting in Cambridge, VOResource v0.1 was presented by Plante as a draft Schema specification, as called for in the work package milestones. The Schema illustrated a model for defining extensions to the generic metadata to describe more specific types of resources such as services or data collections.

Given that VOResource was based on the RSM document, it is also a subject of the resource metadata model review.

2. Identifiers

An important component of registries and resource metadata is the resource identifier, a unique handle for a resource. It not only allows one to unique obtain a resource description from a registry, it also allows a resource description to refer to another resource description. An outline for a standard for IVOA identifiers was worked out within the working group at the Cambridge meeting, and consensus was subsequently reached on the issues over email. Plante is editing the outline into a IVOA Working Draft for a planned release of July 7. We hope to use this document as a test case for the IVOA standardization process.

3. Future Plans

  1. Complete the Resource Metadata Model Review by the end of July; fold results into RM and XML Schema
  2. Idenifier WD:
    • initial version by July 7
    • solicit comments
    • next version targeted for early August
  3. Develop a general style guide for creating metadata schemas in XML in coordination with Data Modeling WG, including an addendum specifically describing how to extend the Resource metadata schema.

Topic revision: r2 - 2003-07-02 - RayPlante
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