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One little bit of goodness that has percolated out from my group at $work in collaboration with the California Digital Library is the BagIt spec (more readable version). BagIt is an IETF RFC for bundling up files for transfer over the network, or for shipping on physical media. Just yesterday a little article about BagIt surfaced on the LC digital preservation website, so I figure now is a good time to mention it.

The goodness of BagIt is in its simplicity and utility. A Bag is essentially: a set of files in a particular directory named data, a manifest file which states what files ought to be in the data directory, and a bagit.txt file that states the version of BagIt. For example here’s a sample (abbreviated) directory structure for a bag of digitized newspapers via the National Digital Newspaper Program:

mybag
|-- bagit.txt
|-- data
|   `-- batch_lc_20070821_jamaica
|       |-- batch.xml
|       |-- batch_1.xml
|       `-- sn83030214
|           |-- 00175041217
|           |   |-- 00175041217.xml
|           |   |-- 1905010401
|           |   |   |-- 1905010401.xml
|           |   |   `-- 1905010401_1.xml
|           |   |-- 1905010601
|           |   |   |-- 1905010601.xml
|           |   |   `-- 1905010601_1.xml

The manifest itself is just the relative file path, and a fixity value:

ea9dee53c2c2dd4027984a2b59f58d1f  data/batch_lc_20070821_jamaica/batch.xml
72134329a82f32dd44d59b509928b6cd  data/batch_lc_20070821_jamaica/batch_1.xml
dc5740d295521fcc692bb58603ce8d1a  data/batch_lc_20070821_jamaica/sn83030214/00175041217/1905010601/1905010601_1.xml
e16e74988ca927afc10ee2544728bd14  data/batch_lc_20070821_jamaica/sn83030214/00175041217/1905010601/1905010601.xml
fd480b2c4bcb6537c3bc4c9e7c8d7c21  data/batch_lc_20070821_jamaica/sn83030214/00175041217/1905010401/1905010401.xml
e0e4a981ddefb574fa1df98a8a55b7a4  data/batch_lc_20070821_jamaica/sn83030214/00175041217/1905010401/1905010401_1.xml
c8dffa3cdb7c13383151e0cd8263d082  data/batch_lc_20070821_jamaica/sn83030214/00175041217/00175041217.xml

The manifest format happens to be the same format understood and generated by the common unix (and windows) utility md5deep. So it’s pretty easy to generate and validate the manifests.

The context for this work has largely been NDIIPP partners (like CDL) transferring data generated by funded projects back to LC. Although it’s likely to get used in some other places as well internally. It’s funny to see the spec in its current state, after Justin Littman rattled off the LC Manifest wiki page in a few minutes after a meeting where Andy Boyko initially brought up the issue. Andy has just left LC to work for a record company in Cupertino. I don’t think I fully understood simplicity in software development until I worked with Andy. He has a real talent for boiling down solutions to their most simple expression, often leveraging existing tools to the point where very little software actually needs to be written. I think Andy and John found a natural affinity for striving for simplicity, and it shows in BagIt. Andy will be sorely missed, but that record store is lucky to get him on their team.

There are some additional cool features to BagIt, including the ability to include a fetch.txt file which contains http and/or rsync URIs to fill in parts of the bag from the network. We’ve come to refer to bags with a fetch.txt as “holey bags” because they have holes in them that need to be filled in. This allows very large bags to be assembled quickly in parallel (using a 100 line python script Andy Boyko wrote, or whatever variant of wget, curl, rsync makes you happy). Also you can include a package-info.txt which includes some basic metadata as key/value pairs … designed primarily for humans.

Dan Krech and I are in the process of creating a prototype deposit web application that will essentially allow bags to be submitted via a SWORD (profile of AtomPub for Repositories) service. The SWORD part should be pretty easy, but getting the retrieval of “holey bags” kicked off and monitored propertly will be the more challenging part. Hopefully I’ll be able to report more here as things develop.

Feedback on the BagIt RFC is most welcome.

Thanks to a tip from Ian, I’m looking forward to (hopefully) attending the Linked Data Planet conference in New York City as a volunteer. The idea is that I just have to pay for my hotel, and the cost of admission is waived. It seems my travel money is a bit limited at the moment (sometimes it’s there, sometimes it isn’t), so I figured minimizing costs would be appreciated. But today I got a request to “justify” my attendance at the conference. It was actually kind of a good exercise to sit down and write why I think the conference and Linked Data in general is important to the Library of Congress.

One of the challenges of Digital Repository work is modeling the context for digital objects. The context for a digital object includes the set of relationships a particular digital object has with other objects in the repository. 30 years of relational database research and development have allowed us to do this modeling pretty effectively within the scope of a particular application.

Very often, particularly in institutions the size of the Library of Congress, the context for a digital object includes digital objects found elsewhere in the enterprise–in other applications, with their own databases. In addition some institutions (like LC) also need to make their digital resources available publicly for other organizations to reference. The challenge here is in making the objects found in silos or islands of application data (typically housed in databases) reference-able and resolvable, so that other applications inside and outside the enterprise can use them.

As a practical example, a picture of Dizzie Gilliespie found in the America Memory collection

is related to the book:

To be, or not–to bop: memoirs / Dizzy Gillespie, with Al Fraser.

which we have described in our online catalog. The person Dizzy Gillespie is also represented in LC’s name authority file with the Library of Congress Control Number n50033872, and the Linked Authority File at OCLC. And perhaps this picture of Dizzie Gillespie in American Memory will find it’s way into the World Digital Library application that is currently being built. How can we practically and explicitly identify and then represent the relationships between these resources? Is it even possible?

The Linked Data Planet conference is a two day workshop describing how to use traditional web technologies in conjunction with semantic web technologies (RDF, OWL, SPARQL, RDFa and GRDDL) to enable this sort of linking of resources inside particular applications, within the enterprise and around the world. My hope is that the conference will provide guidance on simple things LC can do with web technologies that have been in use for 20 years, to model the relationships between digital resources at the Library of Congress.

Hopefully that will convince them :-)

Apologies to Madonna for the blog post title…

Recently there was a bit of interesting news around a MARBI Discussion Paper 2008-DP04 regarding semweb technologies at LC.

Related to this work are RDF/OWL representations and models for MODS and MARC, which we are also developing. Several representations of MODS in RDF/OWL, such as the one from the SIMILE project, have been made available as part of various projects and we have found they useful for our analysis and to inform our design process. We want to bring them together into one easily downloaded and maintained RDF/OWL file for use in community experimentation with RDF applications. Our time line is to have the MODS RDF ready for community comment by June.

access accessible addition al american analysis application applications appropriate archives areas association authority available based benefit benefits bibliographic broad broader catalog catalogers cataloging catalogs cataloguing chain change changes classification code collaboration collections committee communities community congress consequences consider considered content continue control controlled cooperative cost costs create created creating creation current data databases dc description descriptive desired develop developed development different digital discovery distribution dublin ed education effort encourage enhance environment et evidence exchange exist findings focus format formats frameworks frbr future greater group headings hidden identifiers identify ifla impact include including increase increasingly information institution institutions international knowledge language lc lcs lcsh libraries limited lis maintaining make management marc materials metadata model national need needs networks new number oclc online organization organizations outcomes outside participants particular pcc possible potential practice practices primary principles process processes production program programs provide public publishers quo range rare rda recommendations records reference relationships report require requirements research resource resources responsibility results role rules search serve service services share shared sharing sources special specific standards states status subject supply support systems technology terms time today tools types unique united university use used users using value variety various vendors vocabularies washington ways web working works

same stats as before, but the top 200 this time, and as a cloud. It’s crying out for some kind of stemming to collapse some terms together I suppose…but it’s also 3:17AM.

I converted the pdf to text file called ‘lc’ with xpdf and then wrote a little python:

#!/usr/bin/env python
 
from urllib import urlopen
from re import sub
 
stop_words = urlopen('http://www.dcs.gla.ac.uk/idom/ir_resources/linguistic_utils/stop_words').read().split()
text = file('lc').read()
 
counts = {}
for word in text.split():
    word = word.lower()
    word = sub(r'\W', '', word)
    word = sub(r'\d+', '', word)
    if word == ''  or word in stop_words: continue
    counts[word] = counts.get(word,0) + 1
 
words = counts.keys()
words.sort(lambda a,b: cmp(counts[b], counts[a]))
for word in words[0:100]:
    print "%20s %i" % (word, counts[word])

Does me writing code to read the report count as reading the report? …

I opened the paper this morning to read a story of another person involved in the creation of MARC who has just died. I hadn’t realized before reading Henrietta Avram and Samuel Snyder’s obituaries that there was a bit of an NSA LC connection when MARC was being created.

From 1964 to 1966, [Samuel Snyder] was coordinator of the Library of Congress’s information systems office. He was among the creators of the library’s Machine Readable Cataloging system that replaced the handwritten card with an electronic searchable database system that became the standard worldwide.

I imagine NSA folks had a lot to do with early automation efforts in the federal government…but it’s still an interesting connection. One of my coworkers is reading up on this early history of MARC so this is for him in the unlikely event that he missed it…email would probably have worked better I guess, but I also wanted to pay tribute. Libraries wouldn’t be what they are today without this influential early work.