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KMR Group, CSC, KTH (Royal Institute of Technology), Sweden
|Status of Document:||This is a DCMI Recommended Resource|
|Description of Document:||This document describes the Singapore Framework for Dublin Core Application Profiles as presented at the International Conference on Dublin Core and Metadata Applications in Singapore, September 2007. The purpose of this document is to provide a stable and citable point of reference for the Singapore Framework.|
The Singapore Framework for Dublin Core Application Profiles is a framework for designing metadata applications for maximum interoperability and for documenting such applications for maximum reusability. The framework defines a set of descriptive components that are necessary or useful for documenting an Application Profile and describes how how these documentary standards relate to standard domain models and Semantic Web foundation standards. The framework forms a basis for reviewing Application Profiles for documentary completeness and for conformance with Web-architectural principles.
This document provides a summary of the framework. Future documents are planned for providing guidance in creating the necessary documentation.
The term profile is widely used to refer to a document that describes how standards or specifications are deployed to support the requirements of a particular application, function, community, or context. In the metadata community, the term application profile has been applied to describe the tailoring of standards for specific applications.
The DCMI Abstract Model, published as a DCMI Recommendation in March 2005, provides a metadata model of the kind required for formalizing a notion of machine-processable application profiles. In September 2007, Mikael Nilsson presented a framework for the definition of Dublin Core Application Profiles at the International Conference on Dublin Core and Metadata Applications in Singapore (dubbed the "Singapore Framework").
The process of "profiling" a standard introduces the prospect of a tension between meeting the demands for efficiency, specificity, and localization within the context of a community or service on the one hand, and maintaining interoperability between communities and services on the other. Different metadata standards may provide different levels of flexibility: some standards may be quite prescriptive and leave relatively few options for customization, while others may present a broad range of optional features which demand a considerable degree of selection and tailoring for implementation.
It is desirable to be able to use community- or domain-specific metadata standards - or component parts of those standards - in combination. The implementers of metadata standards should be able to assemble the components that they require for some particular set of functions. If that means drawing on components that are specified within different metadata standards, that should ideally be possible. They should also be safe in the knowledge that the assembled whole can be interpreted correctly by independently designed applications. The metaphor of the Lego set has been used to describe this process: an application designer should be able to "snap together" selected "building blocks" drawn from the "kits" provided by different metadata standards to build the construction that meets their requirements, even if the kits that provide those blocks were created quite independently.
In a Dublin Core Application Profile, the terms referenced are, as one would expect, terms of the type described by the DCMI Abstract Model, i.e. a DCAP describes, for some class of metadata descriptions, which properties are referenced in statements and how the use of those properties may be constrained by, for example, specifying the use of vocabulary encoding schemes and syntax encoding schemes. The DC notion of the application profile imposes no limitations on whether those properties or encoding schemes are defined and managed by DCMI or by some other agency: the key requirement is that the properties referred to in a DCAP are compatible with the notion of property in the Resource Description Framework.
It is a condition of the abstract model that all references to terms in a Dublin Core metadata description be made using URIs. Once identified using URIs, terms may be drawn from any source and references to those terms can be made without ambiguity. This set of terms can be regarded as the "vocabulary" of the application or community that the application profile is designed to support. The terms within that vocabulary may also be deployed within the vocabularies of many other DCAPs.
It is important to realize that the semantics of the terms used in application profiles is carried by their definitions, which are independent of any application profile. Semantic interoperability is addressed outside of the realm of application profiles and therefore works across application profiles. An application profile describes the set of guidelines, description rules, and constraints used in creating a specific set of metadata records. As semantic interoperability is provided by a correct use of terms defined in one or more vocabularies, application profiles are about providing high-level syntactic or structural interoperability in addition to the semantic interoperability.
The functional requirements of a Dublin Core Application Profile describe the functions that the application profile is designed to support, as well as functions that are out of scope.
The functional requirements form the basis of evaluating the application profile for internal consistency and for giving guidance on the appropriateness of the application profile for a given use.
The domain model defines the basic entities described by the application profile and their fundamental relationships. The purpose of the domain model is to define a basic scope for the application profile.
The domain model can be expressed using just text or using a more formal approach such as UML.
A Description Set Profile (see [DSP]) defines a set of metadata records that are valid instances of an application profile. The Description Set Profile model is currently being developed within the Dublin Core Architecture Forum and is in progress of being put forward as a DCMI Working Draft.
The Dublin Core Description Set Profile model is designed to offer a simple constraint language for Dublin Core metadata, based on the DCMI Abstract Model A DSP constrains the resources that may be described by descriptions in a description set conforming to the application profile, the properties that may be used, and the ways a value may be referenced.
The optional usage guidelines describe how to apply the application profile, how the used properties are intended to be used in the application context etc.
The optional encoding syntax guidelines describe any application profile-specific syntaxes and/or syntax guidelines, if any.
The figure also shows how the components of a Dublin Core Application Profile relate to "domain standards" -- models and specifications in broader use by communities -- and to the W3C standard Resource Description Framework (RDF), the default foundation for machine-processable semantics in our time.
Description Set Profiles are based on the DCMI Abstract Model (DCAM) inasmuch they specify how the entities of the DCAM are used in a specific set of metadata. In this sense, the DCAM constitutes a broadly recognized model of the structural components of metadata records. The DCAM, in turn, is grounded in RDF.
Description Set Profiles typically use properties and classes defined in standard Metadata Vocabularies such as the DCMI Metadata Terms. Metadata Vocabularies, in turn, are expressed on the basis of the RDF Vocabulary Description Language (also known as RDF Schema, or RDFS).
The Domain Model used in an application is often based on a domain model in wider use; for example, the generic model Functional Requirements for Bibliographic Records (FRBR) is an important point of reference for resource description in the library world.
Guidelines for expressing a specific Description Set Profile in a specific data format may be based on one of several specifications published by DCMI to provide guidance on expressing Dublin Core metadata using common data syntaxes such as HTML, XML, and RDF/XML.
As the Singapore framework is still young, there are no stable, published examples of full-blown application profiles that conform to these guidelines. At the International Conference on Dublin Core and Metadata Applications in Singapore, however, work on aligning the in-progress ePrints applications profile with the Singapore Framework was presented; a slide presentation is available. An experimental model in a specialized wiki syntax is also available for the ePrints application profile.
2008-11-03. Added Status line to header.
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