Models
Models are primal in the creation or conceptualisation of controlled vocabularies (ontologies). Some are used for the validation of vocabularies (schemas), while others can be derived from them. Still others define how given vocabularies are to be useful for subsequent IT purposes (application profiles).
A schema (XML Schema / XSD file) is a machine-readable representation/description of either the actual or the potential data content in a separate file that complies with it. In other words, it is the set of semantic and sequential instructions that can either be used to control the input stored in a given file, or to connect a file that complies with those instructions to an information exchange system or application.
An ontology – within the scope of computer science and, more specifically, as understood for the semantic web information exchange technology – is defined as a formal specification for the purpose of delimiting and grouping facts, events, entities or elements (which we usually categorise as ‘concepts’), based on their common types, properties and interrelationships.
Controlled vocabularies are machine-readable datasets. In order to be presented in human readable form (document format), they require processing based on style sheet rules. This can be achieved by different transformation methods, one of which uses cascading style sheets (CSS). Predefined CSS files are provided here for download.
An application profile (AP) describes how a standard is to be applied in a particular domain or application. Standards typically do not contain constraints such as cardinality; these constraints are defined in the application profile. An application profile only applies to a specified domain. For example: The DCAT-AP is an application profile that specifies how the DCAT standard is to be used in the context of European data portals. An application profile must be accompanied with explanatory documentation.