Due to the complexity of the DOD (Department of Defense) doing research to obtain classified and unclassified documents is a very difficult job, and unless you undertake the research yourself many may fail to appreciate the amount of effort required to obtain any documentation or information via the FOIA (Freedom of Information Act )
The DOD uses various types of database systems, including NIRPNET (for unclassified information), SIPRNET (for SECRET information), JWICS (for TOP SECRET and SCI), skiweb (for processing OPREPs) and Cavenet (for historical information) to name just a few.
In order to access the information within these data bases one must learn how these systems function, the terminology used by the DOD internal communications, and the parameters need to conduct an appropriate search. This in itself is a tremendous task to accomplish, since between different Commands and DOD entities different jargon’s are in use in the form of code words, acronyms and nicknames. Also an understanding of specific designations and contract numbers is required for OPREPs (Operational Reports) for example.
You may also find that certain DOD entities refer you to the National Archives for records, which sometimes leads to no records being found such as those that were generated by the defunct USSPACECOM (US SPACE COMMAND), the whereabouts are still being looked into.
It is a vast problem in trying to identify specific documents unless you have exact location, and specific designations pertaining to documents generated by the DOD, even if you provide their own documentation sometimes they may not find the information you requested originally. This has happened to me on a few occasions. The famous AFI (Air Force Instruction) 10-206 pertaining to the reporting of CIRVIS material which included unidentified flying objects disappeared from this instruction when a updated version was introduced, yet the USAF could not find the authorisation which is required by their records program instruction, this is still in the appeals stage at the Pentagon.
Unfortunately it is the requester that has to reasonable describe the records and the burden of proof is also the requester’s responsibility. Due to the regulations limitations, common sense isn’t in the view of the FOIA officers in general who process the records.