Use of the Dublin Core Abstract Model, Element Set, and Property Refinement model

The Dublin Core Metadata Inititative (DCMI) Abstract Model (DCAM) provides a generic framework for the definition of models that can be subsequently represented using a wide range of interoperability technologies, including both RDF and XML. While DCAM is based on many of the underlying concepts of the Semantic Web, it does not require the use of semantic web technologies in implementation. One of the reasons for adopting DCAM is that the resulting definitions can be flexibly adapted onto different contemporary technologies without requiring any re-engineering of the original models.

Unlike typical Model Driven Architecture approaches, DCAM is based primarily upon web architecture. This makes it easier to map DCAM models into existing web technologies than a pure MDA Platform Independent Model (PIM).

While there is a lot of detailed modelling within DCAM, at a general overview level, DCAM provides a framework for modelling the most common concerns within a specification:

1. The resources, or classes of entity, that are to be described
2. The properties of the resources
3. Encoding schemes such as vocabularies and syntax definitions that refine properties

By addressing these concerns in a common fashion at the model level, interoperability, transclusion and crosswalks between different profiles is facilitated at the binding level. By contrast, one of the most common problems in existing educational technology specifications is the lack of common models underlying different specifications, creating semantic ambiguity when mixing, reusing or mapping elements from different specifications. (See Mikael's paper).

DCAM also promotes the use of type refinements and polymorphism for properties. For example, if a requirement is for a "Description of facilities" property, then this can be represented as an extension of the more generic "Description" property. Implementations can thereby leverage their existing capability for processing more generic specifications, and handle instances containing unknown refinements by processing them according to their supertype. This mechanism is available within the RDFS and W3C Schema languages, and Dublin Core offers implementation patterns for using them.

Common open-source toolkits such as the Apache XMLBeans framework enable such structures to be transparently mapped into programming language concepts.

For example:

<description xsi:type="ext:descriptionOfFacilities"/>

Can be processed using:

if (description instanceof DescriptionOfFacilities){
	//process as facility details
} else {
	//process as general description
}

This approach enables generic models to be readily adapted to new contexts, such as new markets, applications, or jurisdictions, without any modification of the original specification. This process is far simpler and degrades from elegantly than traditional approaches to "application profiling" based on highly elaborate XML models, and promotes a minimal core model rather than a maximal vocabulary.

In addition the DCAM, Dublin Core also offers the Dublin Core Element Set (DCES, also available as ISO 15836). DCES defines a small number of very common reusable properties, such as "title", "description", "identifier", "type" and so on. These properties can be reused in other specifications; when used with property refinement, this enables flexible processing options for implementations, with heuristics for interpreting data that has been created using refinements for use in different markets.

For example, while instances of learning opportunity descriptions may be created within a national context using nation-specific property refinements, these can be aggregated and processed on a European level by applying the semantics of the model upon which such refinements have been layered. This is possible without requiring prior knowledge of refinement schemes. E.g. a European aggregator can process the following elements with no knowledge of any of the schemes used:

<provider xsi:type="en:HEI-C">
	<specification>	
		<instance>
			<dc:subject xsi:type="x1:R306">Accounting</subject>
			<prerequisite xsi:type="xcri-terms:entryRequirements">...
			<dc:description xsi:type="ects:studentFacilities">...
			<places xsi:type="n3:fte">200</places>
		</instance>
	</specification>
</provider>

In summary, use of the DCMI Abstract Model enables a number of benefits to be realized for a new specification.