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An overview of the Metadata schema core is shown by the UML diagram below (Fig 1). The UML illustrates the main classes (entities) and does not show the detailed definitions such as rdfs:label rdfs:comment. Each block represents a class, and it contains a list of attributes of such class (properties). If a class is connected to another class by a closed arrow, it means that it inherits all properties from the other class (e.g. dcat:DatasetSeries inherits from dcat:Dataset which inherits from dcat:Resource). The other arrows, represent relations and contain the type of relation (e.g. dcat:Dataset is connect to a dcat:DatasetSeries via the predicate dcat:inSeries) and the cardinality (e.g. dcat:Dataset can be connected via dcat:inSeries to zero or more dcat:DatasetSeries).

Recommended Versus Mandatory

In line with dcat-ap specification, we make distinction between recommended and mandatory elements (class, and properties). In the following sections, classes and properties are grouped under headings ‘mandatory’, ‘recommended’. In future we might have a third category 'Optional'.

In the data exchange scenario, these terms have the following meaning:

• Mandatory class: a receiver of data MUST be able to process information about instances of the class; a sender of data MUST provide information about instances of the class

• Recommended class: a sender of data SHOULD provide information about instances of the class; a sender of data MUST provide information about instances of the class, if such information is available; a receiver of data MUST be able to process information about instances of the class.

• Optional class: a receiver MUST be able to process information about instances of the class; a sender MAY provide the information but is not obliged to do so.

• Mandatory property: a receiver MUST be able to process the information for that property; a sender MUST provide the information for that property.

• Recommended property: a receiver MUST be able to process the information for that property; a sender SHOULD provide the information for that property if it is available.

• Optional property: a receiver MUST be able to process the information for that property; a sender MAY provide the information for that property but is not obliged to do so.

Diagram

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Terminology

According to DCAT-AP:

• An Application Profile is a specification that reuses terms from one or more base standards, adding more specificity by identifying mandatory, recommended and optional elements to be used for a particular application, as well as recommendations for controlled vocabularies to be used.

• A Dataset is a collection of data, published or curated by a single source, and available for access or download in one or more formats. A Data Portal is a Web-based system that contains a data catalogue with descriptions of datasets and provides services enabling discovery and reuse of the datasets.

Used Prefixes

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