Typically, numerous parameter values are allocated to an Item Type, and certain instances of Items may deviate from the others in terms of specific parameter values.
To capture variations of an Item Types Parent/Child relationships for Items can be used.
This approach enables the creation of multiple "Child Items" belonging to the same "Type" as the Parent Item, while allowing differences in certain instance properties. Example using a Chair as parent Item:
The child Items inherit the specifications from their parent, meaning they will adopt any item data assigned to the parent unless it is specifically overridden or specified for the child (similar to derived Room Data). This inheritance can be extended to an unlimited depth, allowing for versatile customization.
For instance, an office chair with various variants. Instead of creating separate Items for each variant, a single parent Item can be created and define the specifications. Subsequently, child Items are created for the different variants used in the project. Any modifications made to the description will automatically apply to all the children, unless a specific value is provided for a particular child, thereby overriding the inherited data.
The specification is then inherited down. Different values can be added to the children and additional data can be overwritten from either the parent or grandparent thus creating different variants. When looking at the Item data, inherited values will be displayed as normal values, and the unique values for the child will be marked by a red line. When hover the mouse over any inherited values, the values from the parent Item will be displayed the value is from (parent, grandparent, great-grandparent etc).
It is possible to remove a unique value for a child Item and instead let the value be inherited: Read more Display and edit Overwritten Child Items data
Linking Revit families to items with children
When using parent and child Items, this can also be used to support many to many relationships between dRofus and the model (Revit/ArchiCAD):
In dRofus, it is possible to include more type detail than in the Revit/ ArchiCAD model. E.g. Variations of a laboratory bench where the benches have the same geometry but diverse specifications and thus diverse prices, the bench can be splitted into several child-versions in dRofus, and so have the correct version showing up in the reports, budgets and procurement considerations. At the same time, in the model, you want to keep the generic object; just link the parent Item in dRofus to the family type and there will be no conflict when synchronizing the objects from the model (Revit/ ArchiCAD) to dRofus, as long as the count of Items in dRofus is the same as the count of objects in the model.
You can do the opposite; also, that is, to have a higher level of type detail in the model than in dRofus. E.g. if you have different colors on an object (as type information), but for checks with dRofus you only would like to compare count and ensure it is in the correct rooms. You then create the different variants as child Items in dRofus and link the child items to the model, but in dRofus you place the generic parent object in rooms.
See the user manual for the different add-ons and on how to do this with the add-on.