The Eastern District of Michigan Self-Describing Archive Project

CISS has completed the transfer of our archived cases from the nine-track tapes on which they were originally stored to eight-millimeter tape cartridges. At the same time, the information on the tapes was converted to a new format devised locally. The benefits achieved include:

• The 8mm cartridge can be read directly on delmie, which has no provision for 9-track tapes. When a case is to be restored from the archive, it is no longer necessary to read the tape on spmied and forward the data to delmie over the DCN. Operator effort and DCN traffic are reduced.
• The new format is self-describing. The information on the original archive tapes was stored in a structure described only in the ICMS software, and could not be used or interpreted without access to the proper version of ICMS. The new tapes contain additional information describing their own structure, permitting CISS staff (present or future) or future researchers to interpret the content and reconstruct any case information of interest from the tape alone, even if the ICMS software is unavailable because of disaster, obsolescence, or other cause. We believe the self-describing quality is important in records intended for archival storage.
• The new format permits reloading of cases into ICMS with a simpler and faster procedure, freeing CISS time for other tasks.
• The new format, despite the added information to document the structure, is more space-efficient, representing the entire set of converted archive cases in 359 megabytes, 46% of the original space. (Figures for individual tapes in the set ranged from 28% to 61%.) This efficiency combined with the greater density of 8mm tape allowed us to transfer all thirteen original 700-meter 9-track spools to one 15-meter by 8mm cartridge. (A duplicate is kept off-site.)
• With all archived cases on one tape cartridge, an operator can restore any combination of cases requested by our clients without shuffling tapes during the process, freeing still more CISS time for other purposes.
• The self-describing format helps us maintain backward compatibility. Archives created with a newer version of ICMS may contain case data that were not maintained by earlier ICMS versions, or may structure some data differently. Cases can be restored from older or newer archives without ambiguity or confusion, since each archive file describes the structure with which it was created.
• The self-describing archive tapes can be used by applications other than ICMS. Software deing developed by CISS will scan these tapes and extract index information to create our first merged (live and archived) microfiche index, and the foundation of our public access system.