KindOfQuantities in BIS
The choosing of a KindOfQuantity in a BIS schema needs to reflect the intended level of coordination of the grouping of properties and default display-formatting that it represents. In general, there are three levels of coordination to keep in mind:
- Common across the BIS ecosystem.
- Common across a particular subset of schemas.
- Specific to an iModel Connector or Application.
Common KindOfQuantities across the BIS ecosystem
KindOfQuantities defined in the AecUnits schema shall be referenced by properties whose grouping and default display-formatting are meant to be coordinated across the entire BIS ecosystem, disregarding of the disciplines involved.
As an example, the aecu:LENGTH KindOfQuantity can be referenced by properties in schemas at any layer. If the display-formatting of aecu:LENGTH is changed in an Application, the new display-formatting will apply to values from properties across all disciplines referencing it.
Common KindOfQuantities across a subset of schemas
When the coordination about grouping of properties and default-formatting is only expected among properties in a subset of schemas, it is recommended that a separate schema is introduced to define them.
The RoadRailUnits schema is an example of this kind of coordination. For instance, it defines a rru:LENGTH KindOfQuantity that is referenced by properties in Road & Rail schemas whose display-formatting is expected to change together, separate from the common aecu:LENGTH KindOfQuantity mentioned earlier.
Specific to an iModel Connector or Application
When an iModel Connector or Application faces the need of a special KindOfQuantity not covered by existing lower-level schemas, such special KindOfQuantity shall be defined in a Connector or Application-specific schema. It is still recommended to introduce these special KindOfQuantities into a separate schema in order to achieve better control over schema upgrades.
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Last Updated: 09 January, 2023