Dictionary exchange schema

Describing an external file structure in the dictionary (resource database) might be the most comfortable way for complex external data structures. External files can be defined as structure definitions in the dictionary. Structure definitions for external files may consist of attributes, references and exclusive base structures. External file definitions must not contain relationships or shared base types.

Assigning a data source to a field in an external file is possible by means of the property source definition for properties. The first (and only) source definition for a property is considered as database location for the external field. In order to allow several exchange schemata for an external data structure (e.g. for import and export), the data source name may contain the exchange schema name. calling Property::importData() or Property::exportData() functions allows passing the exchange schema name, in which case the data source with the passed name is used for data exchange.

The data source definition for data exchange (Path/Expression) may contain a path to the database property or an expression (in case of import). It may also contain a constant value (string or number). An empty path in a data source means, that an empty instance has to be created (for collection properties or single references). '*' as data source means that the current data source is used (in hierarchical data exchange).

Properties defined as transient properties are included for export but not for import. Data sources in transient properties must be defined in the scope of the current data type.