How open and expandable is the data model?

The CIDOC CRM (ISO 21127) provides for all concepts and properties of the custom-designed ontology to be modelled as sub concepts and sub properties of the CIDOC CRM. Since the CIDOC CRM perceives itself as a top level ontology, there is wide scope left. In line with the custom-designed ontology, the user is able to decide by himself which concepts and properties he wants to model for the domain.
The WissKI software does not necessarily depend on the CIDOC CRM, however, the use of the ISO standard is recommended due to long term availability and security as well as data portability.