Frequently Asked Questions

[Dclipsham]

This thread will hold answers to frequently asked questions about DROID and PRONOM. It isn't intended for technical assistance (please open a new thread for that), rather to answer frequently asked questions about why things in PRONOM and DROID are the way they are. The thread will grow over time

Q. On the Signature File Archive, some signature file versions are missing, for example there are no versions 14, 15, 87, and other gaps in the sequence. Why is this?

A. There are two main reasons:

1. In the early days releases were on a scheduled month-by-month basis, but sometimes the releases were processed even when no changes at all had been made to the data, so these signature files weren't formally released as contained nothing new.

2. We test 'as we go' during the development of a new DROID signature release, and there is a process of copying new data from our 'Development' database, to our 'Live' database in preparation for release day. When we're ready to release, the button to 'go live' is pressed which creates the new signature file, but before we announce the formal release we test this very thoroughly. On occasion we may uncover some error that had been previously missed. There may also be some other technical reason why the signature file isn't correct.

At this point we can either pull the release entirely and revert to a previous release state, which delays the release by at least a day (potentially over a weekend since we avoid Friday releases where possible) but would retain the correct sequential versioning, or we can simply fix the issue/error and push a new release, which then picks up a new version number, resulting in 'skipped' release numbers. 

Generally our choice is driven by how well flagged a certain release has been - if we've promised people that we'd deliver on a certain day, we'll do the quick option. If we haven't then we're more relaxed about rolling back and delaying the release.

Q. Most formats in PRONOM have an 'fmt/' PUID, but some have an 'x-fmt/' PUID. Why is this?

A. The 'x-' designation to a PUID was intended to indicate that the entry is in a 'test' or 'experimental' state, and was supposed to be for internal-use only. In August 2006, signature release v10 included over 400 new PUIDs and was run as an automatic bulk import of data, but during the release process these 'x-' PUIDs were not converted to standard 'fmt' PUIDs, which meant these entries were made public. 

We later announced our intention to replace these 'x-' PUIDs with conventional ones, however by this point many users of PRONOM had built workflows and processes around these entries so the work involved to correct this for others would not be trivial. A decision was therefore made to retain existing, public 'x-fmt' PUIDs but not to mint any further ones.