Discursive Metadata and Controlled Vocabularies

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Discursive Metadata and
Controlled Vocabularies
Mylonas, Elli
elli_mylonas@brown.edu
Brown University, USA
Wendts, Heidi
heidi_wendt@brown.edu
Brown University, USA
Bodel, John
john_bodel@brown.edu
Brown University, USA
While formulating an Epidoc compliant
template for the encoding of ancient
inscriptions, it became apparent that it
was necessary to accommodate discursive
information about various characteristics of
an inscription as metadata in the header
of a document, and to specify the same
characteristics using a controlled vocabulary,
to facilitate searching, sorting and indexing.
The msDesc features of the TEI guidelines do
not actually allow this type of encoding to
occur in several crucial places. However, it is
possible to achieve both goals by repurposing,
and perhaps straining the usage of some TEI
features. We will describe the problem and our
solution in more detail, in order to document
one project’s solution to a common problem, but
also to suggest that the TEI Guidelines might be
modified to allow this as a more normal use.
Epidoc, a TEI P5 schema that has been
developed for epigraphical and papyrological
materials is widely used for encoding classical
and other western inscriptions. Historically,
there have been two parallel and converging
ways to encode this type of documentary
evidence. The first treats the transcription of
the text together with descriptive information
about the support, context, decoration and
history as content, the way it might be if it
were published in a book, and enclosing it
all within the <text> element. In this type of
encoding the TEI header information is brief,
serving to document the source publication,
and not the inscription. The primary example
of this type of encoding is InsAph, which
originated as the digital version of a print
volume, and represented the publication of
record for its inscriptions. The second approach
treats the text of an inscription as content,
and places contextual information such as the
description of the surface the inscription was
written on, its date, format and origin as
structured metadata in the TEI header. US
Epigraphy, which originated as an aggregation
of inscriptions, most of which had already been
published, is an example of this approach.
These approaches have different advantages:
the first results in a more readable and more
nuanced description of the inscription. The
second, in which the placement of information
is more predictable and controlled, allows better
processing, searching and indexing.
The US Epigraphy project records Graeco-
Roman inscriptions that are known to be in
United States collections so that they may be
located and studied or used in teaching. As
such, the metadata that allows the inscription
to be searched and sorted by its characteristics
is of paramount importance. The project is
developing its corpus using an iterative process,
by which inscriptions are first recorded as an
ID number with bibliographic citations, then
metadata and images are added. Transcription
and more detailed descriptions, a necessarily
slower process requiring more epigraphical
expertise, are added as a third step. This
progression ensures that the corpus is as
complete as possible, and that information is
added in a sequence that provides as much
information as possible about as large a number
of inscriptions as possible.
US Epigraphy, following the TEI P5 version
of the Epidoc schema and encoding practices,
relies heavily on the TEI header and uses the
<msDesc> component of the header to record
metadata about an inscription.
In <msDesc> there are elements to indicate
the genre to which the inscription text
belongs (<msItem class=”xx”>), the type of
support on which it is inscribed (<objectDesc
form=”xx”>) and the material of which it is
made (<supportDesc material=”xx”>). These
three elements are used to indicate parallel types
of information, but unfortunately, they don’t
exhibit parallel behaviors.
<msItem> has an attribute to indicate text
genre and it can accommodate more discursive

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detail in a child <p>. The attribute, @class,
is a specialized attribute of type “data.code”
that allows the msItem to point to a controlled
vocabulary of text genres. This is handled
through a complex mechanism as follows: the
text genres are listed using a <taxonomy>
element in <profileDesc>. <textClass>, also part
of <profileDesc> then points to a genre in the
taxonomy, and msItem/@class in turn, points to
<textClass>. This is complicated, but it allows a
controlled, and less precise value to co-exist with
a more nuanced but less processable description
of the text genre. Also, crucially, it maintains the
controlled list of genres in the document, and
not in the schema.
Conversely, <objectDesc> and <supportDesc>
have specialized attributes @form and
@material whose values belong to the class
“data.enumerated,” forcing their values to be
maintained in the schema. This is undesirable,
as it means that an encoder, or a content
specialist would have to modify the schema
in order to change a controlled vocabulary.
Changing the values in an enumerated attribute
also means that it will no longer be possible
to validate different epigraphical projects with
the same schema, even though their document
structures are fundamentally the same.
The ideal solution is to be able to maintain
taxonomies within the document, and refer
to values within them using an attribute
such as @ana, whose value belongs to
class “data.pointer.” <taxonomy> provides
a powerful and appropriate classification
structure, but in the guidelines it is defined
as containing only information on text genres,
and forming part of the <msItem><textClass>
construct. @ana can point to interpretive
elements such as <interp> and <fs>, but not
<category>, which is the constituent part of
<taxonomy>.
Currently, it is possible to create several
taxonomies, and to access them using the
xi.include mechanism, so that all files and
all encoders are using the same controlled
vocabularies at all times, and updates are
immediate. It is also possible to point to
elements in the taxonomies from <objectDesc>
and <supportDesc> using an @ana attribute,
since @ana is globally available, and points to
a valid URI. However, although this validates,
it isn’t semantically correct according to the
TEI guidelines. A more satisfying solution is
to redefine specialized attributes like @support
and @material to behave like @ana, and be able
to point to controlled vocabularies such a those
contained within <taxonomy>.
It is important, when encoding highly structured
but also potentially idiosyncratic materials,
like inscriptions or papyri, to be able to
use both controlled and full-text descriptions.
This should be enabled by the markup, but
should also be encouraged as good encoding
practice. It is also expedient and easier to avoid
errors for encoders and programmers to have
parallel structures describing similar types of
information.
As corpora like US Epigraphy, InsAph, DDDP
and similar collections become more concerned
with how they will be mined and processed,
and are no longer content with creating digital
facsimiles to facilitate access, this type of
information management is becoming more
important. This poster has focused on a few
elements and their accompanying attributes.
They are not the only places where this problem
arises, however. The solution that is presented
here is by no means an ideal one. Indeed, it
is only permissible insofar as it results in valid
TEI documents. There are several other possible
approaches. The best solution will be one that
results in a set of best practices that can be re-
used in other, similar situations.
References
Epidoc.
http://epidoc.sourceforge.net/
(accessed 11/2/2009).
InsAph.
http://www.insaph.kcl.ac.uk/index.h
tml
(accessed 11/2/2009).
TEI Guidelines.
http://www.tei-c.org/release
/doc/tei-p5-doc/en/html/index-toc.html
(accessed 11/2/2009).
(11/2/2009).
US Epigraphy.
http://usepigrap
hy.brown.edu
.