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This paper by metadata expert Thomas Baker articulates first-step requirements for publishing project and domain specific adaptations of metadata standards in a registry of the European SCHEMAS Project.

By Thomas Baker
Submitted to the DC Registry Working Group, Oct 19 2000

Author's Note:
The paper that follows articulates 'first-step' requirements for publishing project- and domain-specific adaptations of metadata standards ('application profiles') in a registry of the European SCHEMAS Project. Please see the previous message for further context. Comments to dc-registry@mailbase.ac.uk welcome.
________________________________________________

Requirements for Publishing Application Profiles in the SCHEMAS Project Registry

Background
The SCHEMAS Project defines itself as a 'forum for metadata schema implementors' [1]. Its mission is primarily didactic -- to help project implementors understand the overall landscape of metadata standards and metadata-using applications. It aims at promoting good-practice methods for drawing on or adapting those standards, as needed, in the design of their own project- or domain-specific schemas. By registering application profiles, therefore, the SCHEMAS Project wants to help project managers and other implementors discover existing projects in a particular sector or domain and see how those projects are using standards in their metadata. The ultimate goal of these activities is the harmonization of good practice in the use of metadata.

Some Definitions
'Vocabulary terms' (or simply 'terms') are elements, qualifiers, or any other type of word-like entity declared in a namespace or application profile.

'Namespaces' declare the names and definitions ('semantics') of vocabulary terms -- ideally on the Web and in a way that is both human- and machine-understandable. The archetypal example is an RDF schema holding the official names and definitions of the Dublin Core Metadata Element Set at the official Web site of the Dublin Core Metadata Initiative. Individual projects, however, can also set up namespaces to declare the names and definitions of elements they have coined locally.

'Application profiles' (or simply 'profiles') declare which elements from which namespaces a particular application or project underlie the local project schema used for its metadata -- in other words, it 'reuses' semantics from namespaces and repackages them for a particular purpose. Ideally, they are also machine-understandable and Web-accessible.

Minimal Requirements
An application profile should be able (in order of decreasing importance):
1) to declare which elements from which namespaces an application or application community is using in its project- or domain-specific schema.
2) to override the default (i.e., standard) definition or label of a particular element (from the namespace) with a definition or label that makes sense in the local context. For example, a profile for an application for describing collections might redefine the Dublin Core element Title -- officially, 'A name given to the resource' -- with a more restricted local definition: 'A name given to the collection'.
3) to describe the project or application to which it refers. At a minimum, this description should give the name and mission of a project or application. Ideally, it would provide further technical detail about the application environment in which the schema is used.
4) to specify dependencies among vocabulary terms -- for example (in profiles that use Dublin Core), that particular encoding schemes may be used with particular elements.
5) to define multiple entity classes in a particular data model. For example, a given application may need to describe both 'people' (with attributes like name, occupation, and weight) and 'resources' (with attributes like title, subject, and format).
6) to provide guidelines, in free text, about the local use of particular terms.
7) to express controlled vocabularies in a machine-understandable way. For example, if the values of the term 'Economic Sector' are restricted to just 'Agriculture', 'Industry', or 'Services', the profile should be able to declare this.

Advanced Requirements
In addition to simply discovering which terms are being used by whom, it could be useful for profiles to describe, in more detail and in machine-understandable ways, exactly how metadata semantics are used in a particular application. For example, profiles could potentially be used by software for automatically validating the conformance of metadata records. To use an old distinction from the world of markup languages, profiles could be not just 'descriptive' of intellectual content (like SGML), but also provide information that is more 'procedural' (like layout or font tags in HTML). Such profiles could therefore:
1) specify in a standard machine-understandable way that an element is mandatory, optional, or repeatable.
2) specify whether a particular field in the instance metadata records can be freely harvested.

REFERENCES [1] http://www.schemas-forum.org

Mr Baker has also written an interesting article entitled 'A Grammar for Dublin Core' for D-Lib Magazine:
http://www.dlib.org/dlib/october00/baker/10baker.html

____________________________________________________
Dr. Thomas Baker
Thomas.Baker@gmd.de
GMD Library Schloss Birlinghoven
+49-2241-14-2352 53754
Sankt Augustin, Germany
fax +49-2241-14-2619


Information:
Author: Thomas Baker
Web Editor: Robert Whelan
Published: Monday, 23 Oct 2000
Last changed: Tuesday, 9 Oct 2001
Keywords: etb, metadata, schemas, registry, dublin

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