Rome Wasn't Digitized in a Day - Council on Library and Information ...

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generated by the decision tree program (C4.5) were used to determ<strong>in</strong>e the more likely variant. The
authors found that the parallel-text correction rate was consistently higher than the s<strong>in</strong>gle-text
correction rate by between 5 percent and 16 percent. Basel<strong>in</strong>e character accuracy <strong>in</strong> this f<strong>in</strong>al
experiment rose to 99.49 percent.
The ability to search text variants and to automatically collate various editions of the same work <strong>in</strong> a
digital library through the use of OCR and a number of automated techniques offers new research
opportunities. In addition, the work of Stewart et al. provides useful lessons <strong>in</strong> how curated digital
corpora, automated methods, and million-book libraries can be used to create new, more sophisticated
digital libraries:
By situat<strong>in</strong>g corpus production with<strong>in</strong> a digital library (i.e., a collection of authenticated digital
objects with basic catalog<strong>in</strong>g data), exploit<strong>in</strong>g the strengths of large collections (e.g., multiple
editions), and mak<strong>in</strong>g judicious use of practical automated methods, we can start to build new
corpora on top of our digital libraries that are not only larger but, <strong>in</strong> many ways, more useful
than their manually constructed predecessors (Stewart et al. 2007).
Further research reported by Boschetti et al. (2009) was <strong>in</strong>formed by the prelim<strong>in</strong>ary techniques
reported <strong>in</strong> Stewart et al. (2007), but also expanded it s<strong>in</strong>ce the <strong>in</strong>itial work did not <strong>in</strong>clude the
recognition of Greek accents and diacritical marks.
Boschetti et al. (2009) conducted a series of experiments <strong>in</strong> attempt<strong>in</strong>g to create a scalable workflow
for outputt<strong>in</strong>g highly accurate OCR of Greek text. This workflow used progressive multiple alignment
of the OCR output of two commercial products (Anagnostis, Abbyy F<strong>in</strong>eReader) and one opensource
47 OCR eng<strong>in</strong>e (OCRopus), which was not available when Stewart et al. (2007) conducted their
research. Multiple editions of Athenaeus’ Deipnosophistae, one edition of Aeschylus, and a 1475
edition of August<strong>in</strong>e’s De Cogitate Dei were used for the OCR experiments. This research determ<strong>in</strong>ed
that the accuracy of s<strong>in</strong>gle eng<strong>in</strong>es was very dependent on the tra<strong>in</strong><strong>in</strong>g set created for it, but it also
revealed that <strong>in</strong> several cases OCRopus obta<strong>in</strong>ed better results than either commercial option. The
highest accuracy level (99.01 percent), which was for sample pages from the fairly recent Loeb edition
of Athenaeus, was obta<strong>in</strong>ed through the use of multiple progressive alignment and a spell-check<strong>in</strong>g
algorithm. (Accuracy levels on earlier editions of Athenaeus ranged from 94 percent to 98 percent).
The addition of accents did produce lower character accuracy results than those reported by Stewart et
al., but at the same time, accents are an important part of Ancient Greek, and any OCR system for this
language will ultimately need to <strong>in</strong>clude them. This research also demonstrated that OCRopus, a
relatively new open-source OCR eng<strong>in</strong>e, could produce results comparable to those of expensive
commercial products.
While both Stewart et al. (2007) and Boschetti et al. (2009) focused on us<strong>in</strong>g OCR to recognize pr<strong>in</strong>ted
editions of Ancient Greek, a variety of both classical scholarship and document-recognition research 48
has been conducted on the Archimedes Palimpsest, 49 a thirteenth-century prayer book that conta<strong>in</strong>s
erased texts that were written several centuries before, <strong>in</strong>clud<strong>in</strong>g previously “lost” treatises by
Archimedes and Hypereides. This manuscript has s<strong>in</strong>ce been digitized, and the images created of the
47 http://code.google.com/p/ocropus/
48 A palimpsest is a manuscript “on which more than one text has been written with the earlier writ<strong>in</strong>g <strong>in</strong>completely erased and still visible”
(http://wordnetweb.pr<strong>in</strong>ceton.edu/perl/webwns=palimpsest). For a full list of research publications us<strong>in</strong>g the Archimedes Palimpsest, see
http://www.archimedespalimpsest.org/bibliography1.html
49 http://www.archimedespalimpsest.org/