External References
An external
reference is created when one document is dependent on another
document for its solution. If the referenced document changes, the dependent
document changes also.
In an assembly, you can create an in-context
feature on one component that references the geometry of another component.
This in-context feature has an external reference to the other component.
If you change the geometry on the referenced component, the associated
in-context feature changes accordingly.
An in-context feature updates automatically if the update path is available.
The update path is contained in the assembly where you create the reference.
If the update path is not available (for example, if the assembly document
is closed), updating occurs the next time you open the assembly that contains
the update
path.
Update paths for in-context features
are displayed in the FeatureManager design tree of the
assembly. You can hide or show all of these in-context icons by right-clicking
the top-level assembly icon 
and selecting Hide
Update Holders or Show Update
Holders.
You also have
the option to not
create external references when designing in the context of
an assembly.
FeatureManager design tree conventions
In the FeatureManager design tree, any item with an external reference
has a suffix that indicates the status of the reference:
The suffix ->
means that the reference is in-context. It is solved and up-to-date.
The suffix ->?
means that the reference is out-of-context. The feature is not solved
or not up-to-date. To solve and update the feature, open the assembly
that contains the update path.
The suffix ->*
means that the reference is locked.
The suffix ->x
means that the reference is broken.
To list the external references on a part
or feature, right-click the part or the feature or right-click the update
holder , and select List
External Refs.
Related Topics
List External
References
Locking
and Breaking External References
Controlling
Creation of External References
Rules
for External References
External
References - Options
File
Management with External References