One of our objectives within the DESIRE2 project is to develop a ‘metadata registry framework’ which is intended to be a prototype metadata registry with guidelines for use. Our aim is to record information relating to the use of metadata within the various DESIRE services with the intention of benefiting development of software tools within the project, promoting the alignment of metadata usage amongst services, while at the same time disclosing to the wider world information about metadata usage within the project. In addition we hope to contribute to the wider debate on role of registries in a distributed environment.

We have been considering the various aspects of a metadata registry, what information might be contained within the registry and what it might be used for. Our main focus will be on the role of metadata registries for the disclosure of information about the structure and semantics of metadata element sets, but there are other functions that might be fulfilled by the registry such as to facilitate interoperability by the provision of mappings between schemas, to record local usage by collaborating services (e.g. agreements on mandatory fields, agreed rules for metadata content).

The need to manipulate and manage metadata of varied formats is shared by agents both human and software resulting in the requirement for both structured or unstructured data to be made available online for humans or applications to process. Establishing some form of 'metadata registry' seems to offer a way forward. For any particular 'metadata element set' the registry could record designation of content and agreed usage. Any extensions to the format would be recorded, as would agreed mapping between formats. The role of such registries would be both to promote and to inform thereby encouraging the use of standard formats and reducing duplication of effort.

Different models for registries could be envisaged to reflect the variety of organisational interests: registries might be partitioned in a variety of ways, there might be a hierarchy of individual registries, or alternatively an overlapping arrangement for communities of use or other models yet to be established. Distributed domain and regional registries might exist in a mesh with higher level 'global' registries.

It does appear there is some convergence of interest in metadata registries at the moment, coming not just from the digital library community but from a variety of other implementation areas and business groups. The Metadata Registries Workshops held over the last two years brought together people from a wide range of communities including those involved in digital library management, database management, and software engineering; people from research backgrounds, as well as service providers in government, business and educational sectors

This interest has been recognised by the International Standards Organization in particular those individuals involved with development of ISO/IEC11179 : Specification and Standardization of Data Elements, Part 6 of which deals with registration of data elements. The ISO Joint Technical Committee 1, Subcommittee 14 (Data Engineering) proposed the first 'Joint Workshop on Metadata Registries' [2]which was held in Berkeley in xxx and was sponsored by the US Environment Protection Agency, OCLC and the Metadata Coalition. The Second Workshop on registries

These workshops reflect recognition of benefits of alignment of metadata registries focusing on requirements of resource discovery and information services with parallel activities in other areas such as rights management, digital preservation.

The registry might undertake a variety of functions e.g.

• to provide an authority for versions of a format and its individual elements
• to provide precise element definitions
• to inform as regards allowable schemes and values
• to provide mapping from a particular element in one format to elements in other formats
• to inform regarding local extensions
• to offer authoratative multilingual versions

In order to achieve this we need to explore data structures, languages to describe schemas, change control, organisational issues such as management by international communities.

XML and XML/RDF use the namespace mechanism in order to associate element labels with schemas defining element sets. Metadata namespaces must be globally visible and accessible. Within a resource a namespace schema will be declared associating metadata elements with authoratative schema, the namespace URL can refer to a schema which may or may not be machine readable, or the URL can serve just as an identifier. RDF offers possibilities for validating metadata descriptions against machine readable schema.

At the simplest level the registry facilitates

• management of metadata namespace
• disclosure of metadata element definitions (semantics)
• informs potential metadata creators of existing schemas

At a more complex level the registry enables software to:

• Automatically validate metadata
• Automatic equivalencing of fields
• Automatic update of versioning of remote metadata
• Automatic multilingual presentation

• ISO 11179
• RDF schemas
• Searchable database??

• ROADS templates
• DESIRE Quality Vocabularies
• Combine formats
• Local usage of Dublin Core (as used in DESIRE? BIBLINK?)
• ROADS to GILS mappings??
• Others.

• Definition
• Revision control (evolution)
• Alignment
• Interoperability
• Mapping
• Promotion
• Tool creation

The registry must accommodate access from (some of!):

• Human
• Metadata creators (cataloguers)
• Metadata schema creators (standard making bodies)
• Registrants (namespace managers)

• Machine
• Generators
• Editors
• Brokers

Comments on DESIRE objectives.

What metadata schemas do you use within services that come under the DESIRE project umbrella?

Do you have mapping tables you would be willing to register?

Do you have documentation for metadata creators which specifies legal values, schemes, locally specific definitions for particular elements?