Importing small segments of a larger model might introduce unresolved elements into the structure. This can happen when all the following conditions are met:
When there exists an element in the model that refers to another, either through inheritance, ownership or in a folder.
The first element is imported into the model.
The second element does not already exist in the model and is not imported.
This is most likely to occur when using source control where the two elements are in separate version files. Checking out a file imports it into the model. The unimported class is flagged as unresolved during the import and must be resolved. An Unresolved tab is displayed in the model that lists all elements that have yet to be resolved.
Unresolved elements can be introduced in the structure after a partial merge and also when an element templates to an unresolved Primitive type.
The IsResolved property is used to indicate that there are elements in the model that refer to elements that do not currently exist in the imported model. This flag is only visible when set to False and an element is unresolved. The import log warns that an imported element refers to another element that isn’t in the model or interchange file. After the element is resolved, this property can only be changed from False to True. Once resolved, an element cannot be made unresolved again. The best way to resolve a unresolved element is by importing this element
Refer to Resolving Elements Example for more information.