No idea and the VW help does not make it any clearer to me what so ever
Copied from VW 2011
Vectorworks? Referencing Capability
A ?workgroup? is several people who work together on a project. Group members may work on the same file or on different files for the same project. Additionally, it is often necessary to create standard elements and reuse them in different files. It can be difficult to share these standards with other members of a workgroup and to keep up with changes to them.
Referencing is the ability to link the current (target) file to a master file that contains the standards. Layers, classes, and resources (such as hatches, worksheets, or symbols) in other Vectorworks files can be referenced. In Vectorworks Design Series products, image files and PDF files can also be referenced. When a referenced item in a master file changes, the changes are reflected in the target file. Updates to target files can be performed automatically or only when manually requested.
You can reference specific layers with all of the classes and resources used in those layers, as well as any resources from a master file. Workgroup-referenced design layers can be displayed in viewports. Referenced items are indicated in the Resource Browser and in the Organization dialog box by italicized names.
There are two ways to reference design layers:
● In the Vectorworks Fundamentals product, design layers are imported into the target file when they are referenced. For backward compatibility, Vectorworks Design Series products support this method; see Setting the Referencing Options.
● In the Vectorworks Design Series products, the recommended method is to create a design layer viewport and then reference the desired design layers from the master file. See Creating a Referenced Design Layer Viewport for details about this type of reference.
Depending on the type of object referenced, you may be able to update the master file from the target file.
● Resources can be edited or renamed in the target file, and the corresponding resource in the master file is automatically updated. See Referencing Resources.
● Objects on layers referenced with layer import referencing are locked; they can be unlocked and edited in the target file, but the change will not appear in the master file. Moreover, when the target file?s references are updated, referenced items are over-written to reflect the master file. Therefore, any permanent change to a referenced item must be made in the master file.
● Objects on layers referenced in a design layer viewport can not be edited directly, but there is an option to navigate to the master file, make the change, and then return to the target file to view the change.
Keep the following concepts in mind for both design layer referencing methods.
● Drawing information is shared and updated on a layer-by-layer basis.
● For layer import referencing, referenced layers should be treated as read-only layers; any changes to referenced information and any information added to referenced layers are removed the next time the referenced layer is updated.
● Referenced layer names cannot be changed.
● Resources (symbol names) in layers that are referenced from the master file take precedence over resources in the target file.
● If there is a naming conflict with pre-existing symbols or pre-existing layers in the current file, rename the symbols or layers.
● Sheet layer viewports cannot directly reference layers in external master files. If you are using layer import referencing, create a reference to the master file, and select the external layers to import into the target file; then make the imported layers visible in a sheet layer viewport. If you are using design layer viewport referencing (Vectorworks Design Series required), create a design layer viewport from the master file and make the desired layers visible; then make the design layer that contains the viewport visible in a sheet layer viewport.
Workgroup Referencing Strategies
Communication within the workgroup is essential when workgroup referencing is in use. Discuss a strategy for how to name, maintain, and update master files. Keep each other informed of major changes?especially the deletion of a master file or resources, which can affect multiple files.
If either the file name or the location of a referenced file is changed, the reference is broken. Items referenced from that file cannot be updated until the broken reference is corrected.