It is much easier to identify the economic benefits of resource sharing than to enjoy them. The tendency has been to apply the principles of Universal Bibliographic Control for bibliographic data to authority data. I believe that these principles are ill suited to this context and their implementation will prove prohibitively expensive. Even if the coding issue could be resolved retrospectively, the thorny issue of nationality would still remain, as Samuel Johnson noted, The ch ief glory of every people arises from its authors . Individual NBAs would in any case be unable to make their authority files available and it is unreasonable to expect other agencies to defer cataloguing until a name has been established.
Volatility is one of characteristics distinguishing authority data from bibliographic records.
This self-containment means bibliographic records are easily exchangable. Much as we may wish that authority data exhibited such stability, we have to accept that they are subject to change whenever references or source data have to be added or when authors change their names or when a conflict has to be resolved by addition of q ualifying data. If the transnational exchange of bibliographic data is to be facilitated by encouraging consistency in authority data it is essential that users have access t o the latest data. This has not been a significant obstacle to the exchange of bibliographic data, which is normally in one direction only and for which a certain level of degradation can be tolerated. Degradation of authority data is not tolerable because spurious access points may be generated and because the mutability of authority data means that it may be subject to erosion over successive t ransfers.