U.S. Patent No. 7,802,310 is directed to licensing using unique identifiers for computer files based on content of the files (pages 2-4).  Prior art Woodhill stores three levels of information including a highest level of a file name and location and a lowest level storing a binary object hash including a binary object identifier based on a hash applied to content of the file (pages 5-6).  Prior art Stefik discloses authentication control (licensing) using unique identifiers (page 6).  In a previous Federal Circuit decision, the case was remanded to decide where all elements were shown and whether a skilled artisan would make the combination (pages 6-7).  For a comparison of the content-dependent name to compare to values, the board had improperly relied only on prior art Stefik and provided no reasoned motivation to combine (page 7).  On remand, the board concluded that the referencing “necessarily must” be accomplished using comparison of the unique identifies (pages 8-9).  On remand, the board found motivation in including authorization of prior art Stefik to the backup system of prior art Woodhill (page 9).  The inherency finding (“necessarily must” compare unique identifiers) lacks substantial evidence (page 10).  It is possible that Woodhill uses the file name and location rather than the unique identifiers, given the prior art Woodhill teaching of user-specification of the file to be accessed and use of the unique identifies after accessing the file (pages 10-11).

Hindsight: The claims appear to be narrow enough to at least cause problems for the allegation of invalidity.  The claims could have been even more narrow but this may reduce opportunity to show infringement.  Drafting claims restricted to a field of use (e.g., licensing or authorization of access to computer files) may help avoid invalidity while broadly protecting the business of the client.  It may be good to consider including a necessary aspect of implementation in that field of use in the claim.