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•“Preservation” means nothing unmodiﬁed.
• This is why it becomes such a bogeyman!
•Two things you need to know ﬁrst:
• why you’re preserving what you’re preserving, and
• what you’re preserving it against.
•Libraries: your collection-development policy
should inform the ﬁrst question.
• Your coll-dev policy doesn’t include local born-digital or
digitized materials? This is a problem. Fix it.
•The second question is your “threat model.”
Why did I just make you
•I’m trying to destroy the myth that any given
medium “preserves itself.”
•Media do not preserve themselves. People
preserve media—or media get bizarrely lucky.
•We need not panic over digital preservation
any more than we panic about print.
•Approach digital preservation the same way
you approach print preservation.
List important threats
to digital data.
•“It’s in Google, so it’s preserved.” (Not even
•“I make backups, so I’m ﬁne.”
•“I have a graduate student who takes care of
•“Metadata? What’s that? I have to have it?”
•“Digital preservation is an unsolvable problem,
so why even try?” (I’ve heard this one from
librarians. I bet you have too.)
Mitigating the risks:
planning and auditing
• Trusted Repository Audit Checklist
• (If you see “NARA/RLG” somewhere? This is the framework that
evolved into TRAC. Long story.)
• You can get an actual formal TRAC audit from CRL! Who has? Portico,
Hathi, “Chronicle of Life,” two-three others. This audit is HARSH. (So
don’t write oﬀ a repo because it hasn’t had a TRAC audit.)
• If you hear the phrase “trusted digital repository,” it should mean
that the repo has had (or is pursuing) a TRAC audit.
• More ﬂexible, less ﬁnger-shaking than TRAC.
• Less of this “designated community” nonsense.
• Less dependent on OAIS model (which I consider a strength).
• Encourages archives to consider and document their individual
situations and think hard about risk mitigation.
Newer: SPOT model
•Even less clunky than DRAMBORA.
•I quite like this one.
•Identifying Threats to Successful Digital
Preservation: the SPOT Model for Risk
So what do they audit?
•Mission (and adherence to it)
•Plans and policies
• including contingency plans
• including tech infrastructure, service infrastructure
•“Doing the right things with the stuﬀ.”
• identiﬁers, ingest ﬁle format management, migration, etc.
•NOTICE WHAT’S FIRST ON THE LIST.
• remember, the tech part is the easy part!
TRAC, DRAMBORA, and DH
•TRAC, DRAMBORA, and SPOT are designed to
audit repositories, not individual datasets, data
ﬁles, or research projects.
• They assume a lot of infrastructure and (in TRAC’s case) a
long-term time horizon that you probably aren’t.
•So if you’re trying to think through a project,
where do you go?
• TRAC and DRAMBORA are probably overkill!
• (Though parts of DRAMBORA won’t hurt you.)
Data Curation Proﬁles
•Research project out of Purdue’s Digital Data
Curation Center (“D2C2”)
•“Toolkit:” interview instrument, user guide for
interview instrument, worksheet.
•Small library of completed proﬁles
•Ignore the user guide. Grab the worksheet, and
use the interview instrument for reference.
• You have to make a login to download the toolkit pieces.
Physical medium failure
•Gold CDs are not the panacea we thought.
• They’re not bad; they’re just hard to audit, so they fail
(when they fail) silently. Silent failure is DEADLY.
•Current state of the art: get it on spinning disk.
•Back up often. Distribute your backups
geographically. Test them now and then.
• Consider a LOCKSS cooperative agreement. Others have.
•Bitrot-detection techniques may help here too.
•Any physical medium WILL FAIL. Have a plan
for when it does.
•The art and science of investigating digital ﬁle
formats and media.
• Reading obsolete ones.
• Reverse-engineering and/or documenting existing ones so
they don’t go obsolete.
• Ensuring secure deletion, when necessary.
• Reconstructing what used to be on a physical storage
medium. (Surprising how often this is possible!)
• Audit trails for legal and records-management purposes.
• AMAZING report (highly highly recommended!): “Digital
Forensics and Born-Digital Content in Cultural Heritage
pub149abst.html. Both computer-nerdy and humanities-
nerdy in the best possible way.
•Sometimes used for “ﬁle format obsolescence.”
•I use it for “the bits ﬂipped unexpectedly.”
•Checking a ﬁle bit-by-bit against a backup copy
is computationally impractical for every day.
• Though on ingest it’s a good idea to verify bit-by-bit!
• A ﬁle is, fundamentally, a great big number.
• Do math on the number ﬁle. Store the result as metadata.
• To check for bitrot, redo the math and check the answer
against the stored result. If they’re diﬀerent, scream.
• Several checksum algorithms; for our purposes, which one
you use doesn’t matter much.
• “Hash collision:” it’s possible, but unlikely, for diﬀerent ﬁles
to have the same checksum. Potential hack vector!
Migration vs. emulation:
dealing with obsolescence
• change the ﬁle to be usable in new software/hardware
• risks: information loss (FONTS!), imperfect transfer,
choosing the wrong migration path
• smart systems don’t throw away the old ﬁles!
• keep the ﬁle, train new software/hardware to behave like
• risks: imperfect emulation, impractical emulation
• makes more sense for software (games!), less for ﬁles
• Current versions of the original software may be able to
open old ﬁles.
• Open-source software in the same genre may be able to
translate proprietary ﬁle formats (often imperfectly). Tend
to maintain translators longer than you’d think.
• Look on the web!
• MIGRATE FAST. Once it’s damaged or obsolete, it’s
probably too late.
• look for the gamers! it’s WILD what they’ll emulate!
• Look to the open-source community for operating-
system, hardware-driver emulators.
• Frankly, there’s a lot of hype and vaporware here.
When is a PDF not a PDF?
•When it’s a .doc with the wrong ﬁle extension
•When there’s no ﬁle extension on it at all
•When it’s so old it doesn’t follow the
standardized PDF conventions
•When it’s otherwise malformed, made by a
bad piece of software.
•How do you know whether you have a good
PDF? (Or .doc, or .jpg, or .xml, or anything else.)
File format registries and
•JHOVE: JSTOR/Harvard Object Validation
• Java software intended to be pluggable into other
• Answers “What format is this thing?” and “Is this thing a
good example of the format?”
• Limited repertoire of formats
•PRONOM/DROID + GDFR = Uniﬁed Digital
•Wrapper tool: FITS, File Information Tool Set
• JHOVE + DROID + various other testers. State of the art.
•Copyright 2011 by Dorothea Salo.
•This lecture and slide deck are licensed under a
Creative Commons Attribution 3.0 United