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Colum Hourihane
Director, Index of Christian Art
Princeton University
Analyzing the subject matter or iconographic content of images has a
long and distinguished history stretching back to the pioneering efforts
undertaken by scholars such as Cesare Ripa in the seventeenth century.1 From
such beginnings, numerous more or less systematic attempts have been
made to develop structures and approaches for classifying image content
in a number of disciplines, one of the most recent being that of art
history.
Most cataloguing systems
include one or more metadata elements or database fields
for content or subject classification, and the relative position of this
category
or element within the overall structure of the system
is usually indicative of its importance in the entire cataloguing process.
A number of recent
studies have shown the significance of subject access
to images and the importance of this metadata element in the electronic
environment.2After
the element of creator/artist/maker, that of content or subject matter
appears to be the most widely used in online queries for art-historical
material. In other words, many end-users tend to search for art images
using the search criteria who created the work and what is
the work of or about.
The process
whereby the subject matter of an image is described
or catalogued in an objective textual description is
complex. I would argue that, of all the different stages
involved in creating access to an image, that of cataloguing
is the most significant. The cataloguer or iconographer
acts as a conduit between the work of art (or a visual
surrogate of it) and the end-user or researcher. Online
access to the work of art or its content is only as
good as the work done "behind the scenes" by the cataloguer.
These two peoplethe end-user and catalogueras
well as the two stages in which the image is first
viewed by the cataloguer and later retrieved by the
end-user, are totally independent of each other and
usually are separated in time and space; but they are
also indefinably linked by very real levels of verbal
and nonverbal communication. The cataloguer is generally
the only human or subjective element involved in the
classification process, and the ultimate success or
failure of end-user retrieval rests with that individual.
Until the time when content-based image recognition
is more developed,3 the cataloguer will
remain central to the classification process, and it
is only by understanding the approaches and possibilities
involved in the task of cataloguing that we can improve
this crucial stage of creating access to images. Despite
the importance of this individual, I know of no studies
on the role of the cataloguer in the classification
process or on the methodology used in image classification.
This essay is an attempt to describe and understand
that role and that methodology.
The two
elements upon which I believe good cataloguing depends
are structure and methodology, and these
are the focus of my analysis. Structure in cataloguing centers
on the cataloguer's understanding of the general practices
and rules of analysis and classification, as well as
on his or her knowledge, expertise, and experience. Methodology
in cataloguing is in many ways dependent on good
structure in cataloguing and on the cataloguer's understanding
of how to apply metadata standards, controlled vocabularies,
and classification systems. Underlying both should
be the goal of meeting users' needs.
Structure in Cataloguing
Structure for the image cataloguer has to do with the way in which content
is viewed, analyzed, interpreted, and presented. A cataloguer approaches
subject matter in a number of sometimes almost imperceptible stages,
and these must be understood for successful cataloguing and ultimately
successful end-user retrieval. The approach of a general observer, who
may simply look at an image for pleasure or interest, differs significantly
from that of a professional cataloguer, whose main task is to systematically
analyze and classify the elements in an image for eventual use by end-users;
cataloguers make end-user access possible. The cataloguer's perspective
must be that of a "professional" viewer or analyst in which subjective
elements are abandoned and consistency in structure and approach predominates.
While there have been several studies of the psychology of perception
and recognition,4 to my knowledge none has addressed the psychological
processes or methodology of the cataloguer.
Structure in Viewing, Analyzing, and Interpreting
Critical to understanding the actual cataloguing process is the psychology
of approachthe way in which we consciously or subconsciously look at
a work of art and the impact this may have on cataloguing content. The first
stage in the cataloguing process begins with initial exposure to the work,
one of the least understood stages in the entire process. Although this stage
can have a major impact on the end result, it has never been fully researched
or formally incorporated into the cataloguing process, which is usually defined
as beginning with formal analysis and interpretation. Nevertheless, the initial "viewing" processwhich
precedes the more clearly defined and better known stage of subject analysisis
critical from the cataloguer's perspective.
Throughout the following discussion,
it is important to keep in mind that the cataloguer usually works in a controlled
environment in which images must be analyzed and described with little concession
to casual viewing; speed is usually a significant factor. The viewing process
is one in which subjective emotions can affect what is described; it is necessary
to understand what we mentally do when we see a work of art and to understand
how changes in this process differ between the general viewer and the cataloguer.
The viewing process for the general viewer is normally one in which little
structure is imposed; the cataloguer, however, must impose a degree of formality
upon the way he or she views images. General viewers are free to spend as
much or as little time as they want looking, and they are under no obligation
to move beyond what they want to see.
Unlike casual viewers, cataloguers
must train themselves to look at every work of art to be described in
a consistent, ordered, and paced manner. The general viewer can dislike
and
mentally reject
an entire work or certain elements of it or can focus only on those parts
to which he or she can relate, all without affecting anybody else's perception.
But a professional cataloguer's main task is to systematically record
every "important" element
within the work, "translating" these elements from a visual to a textual "language," to
echo Patricia Harpring's observation in the preceding essay in this volume.
In viewing an image, the professional
cataloguer must impose structure not only on the way in which subject
matter is recorded but also on the way the work is viewed. The casual,
random approach
to viewing must be abandoned. The cataloguer must be aware of what
is in the entire image, not just portions of it. Classification must
move
from
a general visual analysis of the work as a whole to a detailed evaluation
of its constituent parts.
In looking at Nicolas Poussin's The
Holy Family (pl. 5), for example, a viewer's eye can immediately focus
on any one of the many rather complicated visual elements in the composition.
It may be the family group on the left to which the eye is first attracted,
or the group of infant boys on the right, or the scene in the background
of a man in a small boat ferrying a woman. The cataloguer must, however,
approach the entire work in a structured and comprehensive manner, first
focusing on the main subject matter and then proceeding to describe its constituent
parts. Using the ICONCLASS system5 to describe this work,
a catalogue entry might read as follows:
73B8211 Holy Family with John the Baptist, Elizabeth present
33A14 embracing (John the Baptist and Jesus)
73B2 adoration of the Christ-child
92D1916 cupids, 'amores,' 'amoretti,' 'putti'
31A5463 towel
41A2415 jug and basin
41A7751 basket
41A645 ruins
41A64 garden ornaments, ewer
41A773 container of ceramics, jar, jug, vase, pot
25I2 village
25G3 tree
43C212 racing on an animal mount
46C1111 crossing a river |
This entry deals primarily with the main subject of the Holy Family
and the significant interaction (embracing) between the two main figures
in this group, the Christ child and the infant John the Baptist. The
next important visual element is the group of putti and their interaction
(adoration) with the Holy Family. From here, classification proceeds
in a clockwise direction to the other elements within the composition.
Such an
approach attempts to include all the main visual elements
that might be of interest to a researcher. Doubtless,
classification could proceed further to include details
such as the types of flowers and plants, but a decision
has to be made as to what is of potential value to
users and what is merely staffagethat is, visual "accessories" with
no particular thematic significance; of course, time
and money also play an important role in limiting the
extent of classification in any given project.
Associated
with the ICONCLASS alphanumeric notations (which can,
and indeed probably should, be "hidden" from the end-user)
and their textual correlates is a rich set of keywords,
which is really what forms the searchable element or
interface to images indexed using the ICONCLASS system.
The keywords for the ICONCLASS notations listed above
include the following:
Bible, New Testament,
Christ, infancy, Christ-child, Mary (Virgin), Joseph
(Saint), Holy Family, John the Baptist (Saint), Elizabeth
(Saint), human being, biology, mind, spirit, expression,
face, mouth, lips, pressing, kissing, society, civilization,
culture, housing, garden, ornaments, cloth, toilet
articles, bathing, washing, hygiene, care, body,
human figure, corpo humano, man, woman, jug, wash
basin, bathroom, ancient history, classical antiquity,
history, mythology, gods, heaven, serving, Cupid,
Love, offspring, companion, train (retinue), cupid,
village, landscape, world, earth, nature, recreation,
movement, speed, games, exercise, sport, animal,
riding, race (contest), transporting, land, road,
ford, crossing a river, traffic
These keywords include high-level concepts such
as "society," "civilization," "culture," and "classical
antiquity" that an end-user would rarely use as
search terms. Nevertheless, such keywords can offer
a way to group items by broad concepts and are
automatically carried along with more specific
keywords such as "kissing," "village," "crossing
a river," and so on.
Cataloguing
the same image using the Garnier system6 presents
us with a different approach, which is interesting
to compare to the ICONCLASS method; in Garnier,
controlled terms are used rather than alphanumerical
notations linked to textual correlates. Although
the Garnier system provides less detail than
ICONCLASS with regard to the main iconographic
theme (the Holy Family), like ICONCLASS it moves
from broad themes, such as "biblical scene," to
specific details, such as "boat" and "horse," as
shown below:
Scène biblique
Sainte Famille7
Sainte Jean Baptiste (le Précurseur)
putti
extérieur: décor d'architecture
rivière
barque
arrivée
cheval
cadre urbain
How
do we structure an approach to viewing an image
as distinct from structurally classifying its content?
The cataloguer first has to control the tendency
to describe by intuition and instead structure
his or her personal perceptions. Structure enables
the cataloguer to methodically, consistently, and
comprehensively view and record every significant
element in the work. Visual content can be "read" as
if it were text. When reading a sentence, for example,
the reader may approach the words from left to
right, right to left, or top to bottom, depending
on the language. But in every case the reader reads
in a consistent and methodical manner, never beginning
from a randomly selected word in, for example,
the middle of a sentence. In the realm of images,
it is possible to read from "the beginning" as
well. It is possible, however, to begin "reading" a
visual work in the middle, as in Islamic manuscript
illuminations showing Muhammad resolving the dispute
at Ka'ba, where the central focus is the figure
of Muhammad and the secondary material revolves
around him; or in crucifixion scenes, where the
main subject in both visual and thematic terms
is the figure of Christ on the cross, which more
often than not occupies a central position in the
work. For works in which the main element is not
at the center of the composition, the approach
of "reading" from left to right or right to left
or top to bottom can be used. This approach can
vary from work to work and clearly depends on the
nature of the particular image; the point is that
there is an ordered manner in viewing and describing
content.
One
of the most structured approaches to reading an
image is the Index of Christian Art at Princeton
University.8 For example, in describing
two panels from the bronze doors created by Andrea
Pisano in 1330 for the Baptistery in Florence (figs.
18, 19), the Index of Christian Art employs a combination
of subject terms and free-text descriptions, as
shown in the following example, which depicts a
typical Work record for the two panels, one showing
the body of John the Baptist being borne to burial,
the other the actual burial. Controlled keywords
and keyword phrases are used in the Subject field,
and free-text descriptions appear in the Description
field.
The Index
of Christian Art subject authority record for the
iconographic theme of the burial of John the Baptist
includes the ICONCLASS alphanumeric notation, textual
correlate, keywords, and bibliographic reference,
in addition to the local controlled keywords ("John
Baptist: burial") and other local data elements,
such as the type of subject:
Every word
in a textual sentence has to be read for sense
to be made of the sentence; the same holds true
for all the elements in a work of art. The initial
viewing of a work of art is a process that corresponds
to a great extent to the first stage in Erwin Panofsky's
three levels of image description, which are discussed
by Sara Shatford Layne and Patricia Harpring in
their essays in this volume. (Initial viewing differs
from Panofsky's "description," however, in that
the viewing process need not necessarily preclude
an element of analysis or interpretation.) Structure
in viewing an image is a learned process that involves
training the brain both to slow its natural inclination
to focus on selected subjective elements and to
see the entirety of the work with all of its constituent
parts.
Reading
an image in an orderly, structured manner can help
ensure comprehensive coverage of every element
from the least significant to the most important.
For example, in Jan Steen's The Drawing Lesson (pl.
6), the work should be read first in terms of the
most important element or activity in the imagethe
actual lesson and those involved in it. The remaining
elements in the image can then be recorded in an
ordered manner, from left to right, if so desired.
Using a series of controlled keywords, the subject
matter of this work might read as follows:
Primary subjects: drawing lesson; artist
training pupils; studio; implements of artist;
Vanitas; personification of time; personification
of temporary nature of art
Secondary subjects: model cast; woodcut;
male nude; sculpture; ox; easel; painting;
musical instrument; violin; canvas; drawing;
carpet; furniture; chest; still life; wreath;
skull; wine; clothing; book; pipe; window;
container; frame; work associated with Jan
Lievens; artist, teaching; drawing; draughtsman;
draftsman; workshop; studio; brush; painters'
tools; pencil; charcoal
Viewing is
a process that rapidly develops into the critical
stage of formal analysis and interpretation, but
it can occur only after all the elements in a work
have been viewed and identified. Analysis and interpretation
are dependent on a number of factors, the most
important of which are the knowledge, skills, and
expertise of the cataloguer. A great deal also
depends on the nature of the material being catalogued.
If the collection is more or less focused on a
particular style, period, or geographic area, and
the end-user is likely to have a similarly specialized
knowledge, then the cataloguer also has to have
more than a passing acquaintance with the subject
to proceed with adequate classification. If the
collection is art-historical in the broadest sense,
however, with no particular focus on period, style,
or geographic area, then a cataloguer with broad
knowledge will offer the best results. By and large,
the best art image cataloguers are generalists
with a good working knowledge of most subjects;
cataloguers with expertise in a particular style
or period may produce records that are too narrowly
focused and that even omit access points that many
end-users would likely use. A general rule might
be to use specialist cataloguers for specialized
collections (or for specific projects with a very
definite focus (for example, images of Hindu gods,
seventeenth-century French decorative arts) and
generalists for more encyclopedic collections.
Good
subject classification demands that every important
element in a work be described first; this corresponds
to Panofsky's "pre-iconographic" level of pure
description. Only after the first phase has been
completed should the cataloguer add a level of
interpretation to the objective description. It
is good practice for the cataloguer to include
broad concepts underlying the more obvious descriptors,
thereby making available searchable terms that
may not be included in the specific terms. For
example, in cataloguing one of William Wegman's
famous images of Weimaraners, a cataloguer might
want to include keywords such as "sporting dog," "dog," "mammal," and "animal,"9 unless
such terms are already included in the syndetic
structure of the thesaurus being used to assist
end-users in their searches.
The
cataloguer does not rely solely on what is represented
in the work of art; he or she also draws on sources
external to the work. External elements can come
from the title of the work, the wall label in a
museum or gallery, a literary work, reference books,
and so on, but the most important external source
is undoubtedly the knowledge from personal experience
and formal education that the cataloguer brings
to an interpretation or analysis of the work. In
terms of access, the most immediate source of knowledge
that can add to our understanding of the work is
usually the title. Even though the title may have
been assigned to the work long after the artist
parted with it and may bear no relation to what
the artist intended, it is usually an invaluable
source of information, particularly in the area
of modern art. When faced with a nonrepresentational
work, such as one of the abstract paintings in
Richard Diebenkorn's famous Ocean Park series,
the title adds a level of meaning that not only
can be recorded in subject classification but also
is more useful than simply classifying the work
as "abstract" or "nonrepresentational." Even when
scholars know that the assigned title of a particular
work does not relate to what the work actually
represents, it is important for the cataloguer
to record the obsolete information. The identification
of sitters can change over time,10 yet,
even when modern scholarship provides irrefutable
proof of another identification, the superseded
name must be recorded as well. One such work is
Rembrandt's painting at the Prado in Madrid. Over
time, its subject has been identified as Lucretia,
Sophonosba, Cleopatra, and, more recently, Artemisia.
The sitter has also been identified as Saskia van
Uylenborch, the artist's wife. Data such as these
should, at all times, be included in the metadata
element or database field dedicated to subject
matter in an information system.
Context
can also add to our understanding of subject
matter. This is particularly true when works are
part of
a narrative sequencethat is, when there
is a broader context or location of which an
individual
work is just a part. For example, sculptural
programs on the exteriors of medieval cathedrals
can provide immediate clues as to the likely
subject matter of an individual sequence. Prophets
are frequently found in the same location, personifications
are similarly grouped in relatively few areas,
and general subjects are nearly always ordered
in an identifiable sequence. Similarly, manuscripts
such as Bibles, missals, and books of hours follow
sequential patterns where context can enlighten
the cataloguer as to the likely subject matter.
Miniatures in such works usually relate to the
text and are likely to be ordered in a set narrative.
Three
additional indirect sources of information for
the cataloguer involve the artist, date, and
style of a particular work of art. As Christine
Sundt points out in the following essay, the
cataloguer can sometimes use these elements to
identify or qualify content and to place the
specific work within the broader framework of
the artist's output.
It
goes without saying that a good library of reference
works appropriate to the material in the image
collection is essential for every cataloguer.
Encyclopedias, geographic and cultural guidebooks,
and dictionaries are essential cataloguing tools.
Along with the standard print publications, cataloguers
should investigate the many electronic resources
that are rapidly gaining acceptance and being
used with greater frequency by increasing numbers
of cataloguers.
Structure in Interpretation
Under ideal conditions, the cataloguer first
views an image and interprets its compositional
elements in light of his or her experience
and knowledge.
An art image cataloguer with a certain cultural and visual background will
immediately recognize, for example, a reproduction of Leonardo da Vinci's Mona
Lisa, a photograph of the Taj Mahal, or an image of a Native American
totem pole. In such cases, recognition and interpretation are immediate
(sometimes even intuitive) and nearly always based on the cataloguer's
knowledge.
When recognition occurs so
quickly, the cataloguer may be unaware of the actual process of interpretation;
it is
not until the process becomes more paced that its stages can be understood.
This happens, for example, when a cataloguer does not recognize the landscape
or the individual represented in a particular image. Then the process of
interpretation begins consciously. There is usually little difficulty
at the initial stage
of analysis, which loosely corresponds to Panofsky's pre-iconographic stage.
At this stage, the cataloguer works from the broadest subjects or concepts
to the most detailed when these are known. When the subject matter is not
known, the iconographer builds toward an interpretation using the most
detailed clues
in the image and approaching a broader interpretation.
One of the great
problems in image classification is the inability
to distinguish between subject
matter and information that tangentially relates
to content, such as the style or the date of a
work of art. The inclusion of such incidental information
in formal classification structures exacerbates
the confusion. In Garnier's system, for example,
style and date are included in the classification
system. Style and date are metadata categories
or elements that relate to object and not to subject
classification. The concept of style should be
included in subject classification when a work
of art with a recognizable style is represented
within the image being classified. For instance,
the subject classification for a seventeenth-century
painting depicting galleries or private collections
in which connoisseurs peruse a large group of paintings
or images of classical architecture by artists
such as Sir Lawrence Alma-Tadema should mention
the style of the paintings represented within the
scene. Otherwise, the concept of style or school
or date should be recorded in metadata categories
(and the fields in a database or information system
that correspond to those metadata categories) other
than the category intended for recording subject
matter.
It
is easy to classify subject matter in terms of
what is identifiable in an image; the two major
difficulties lie in deciding what should not be
included and in attempting to classify concepts
that are not explicitly represented. If it is difficult
to distinguish what should not be included, it
may be easier to decide what should. An unwritten
rule in subject classification is to include even
the minutest detail as long as this detail is depicted
with sufficient clarity to potentially be of value
to end-users. The users' needs should always determine
whether an element should be recorded. Experience
has shown that users rarely look for a single element
at a time; they are usually seeking what they request
in their query in combination with some unstated
element or elements.
A
major difficulty arises when the cataloguer is
faced with the need to encode abstract concepts,
ideas, or emotionswhat Panofsky called the iconology of
a work of art. A prominent characteristic of Victorian
art, for example, and one that is frequently of greater
importance than the recognizable elements in individual
works, is the moral message or didactic purpose behind
the artist's image. Objective elements in a work
of art can be easily classified, but it is frequently
impossible to specify exactly what was intended when
it comes to the more abstract messages that the artist
wished to convey. The dividing line in visual representations
of emotions or abstract concepts such as despair,
sadness, destitution, poverty, and isolation is extremely
fine, so it is important to include as broad a range
as is practical.
Cataloguers
should always try to put themselves in the place
of their end-users with regard to the value of seemingly
insignificant elements in an image. Qualifiers such
as position, detail, and relationship with other
elements can be used to gauge the importance of such
elements in a visual work. The argument to exclude
insignificant elements is stronger when they are
clearly background details or staffage. As a general
rule, however, if a detail can be specified, then
it should be. Moreover, details should be either
included or excluded as standard practice rather
than according to the likes or dislikes of the individual
cataloguer.
This
element of consistency is important, especially in
classification systems that allow the cataloguer
to enter specific details. In most classification
systems, the cataloguer can enter the details of
generic objects that are specific to the work being
catalogued. The names of people, bridges, or cities
may be listed, or the scene from a Shakespearean
play, to give just a few examples. It is important
in such instances to structure the details consistently
and to use interchangeable international standards
wherever possible.
Methodology in Classification
Closely related to the way in which the cataloguer approaches content is how
that content is recorded and the standards that are used. The importance
of standards cannot be overemphasized. For the cataloguer, standards exist
both in the systems that can be used to classify subject matter and in how
those data are structured within these systems. Whatever cataloguing structure,
vocabulary and classification tools, and information system are selected
for a descriptive cataloguing project, it is imperative that sharing information
in the broader community be considered and enforced from the start.
Whereas most of the standards
used to classify art-historical content have been specifically developed for
this purpose (unlike the early days, when bibliographic standards were applied
to visual material), many have been adopted from the broader information universe
and include, for example, standards such as the Anglo-American Cataloguing
Rules.11
Once cataloguers
recognized that textual and visual materials are vastly different, systems
of subject classification began to proliferate, and they continue to develop
at an alarming rate.12 And once cataloguers began harnessing
information technology for art-historical classification, interest in classifying
content was renewed, which has led to the wheel being constantly reinvented.
Systems have either been collection-generated or structured independently
of any particular collection of objects or visual materials. The former,
which outnumber the latter, are more specific in focus, with narrower applications.
The latter, which include ICONCLASS, the Garnier system, and the Art & Architecture
Thesaurus (AAT), attempt to be much more inclusive. Increasingly, museums
and image archives have been building classification systems and indexes
specific to their own collections, populating them with data values taken
from systems such as ICONCLASS or the AAT. Some vendors of collection management
systems now offer both a thesaurus construction module and structured vocabularies
(such as the AAT) "built in" to facilitate populating local authorities
or classifications with terms from recognized, standard vocabularies.
Classification systems can
and in fact should differ in the way in which they are applied by cataloguers
and indexers, and the way in which they are made available to end-users.
When used to tag or index items in an information system, classification
systems and vocabularies must be rigorously applied and need not be user-friendly,
except to the professional cataloguers using them. The public face of such
structures must be user-friendly and easy to understand, however. ICONCLASS
is an example of such a dual-natured system, where the cataloguer applies
a series of alphanumeric notations or codes that would be off-putting as
well as meaningless to an end-user. End-user access to these notations
is made possible through a series of natural-language keywords, rather
than through the forbidding alphanumeric codes.
Classification systems can
use free-text descriptions or controlled vocabularies, not that the former
preclude control. Each has its own particular value, and the ideal is
one where both approaches are used and complement each other.13 Free-text
descriptions enable the cataloguer to give an unrivaled mental image
of the subject matter of the work of art and, in particular, to describe
the
relationship of elements to one another within the work. The location
of a particular subject in the image ("left foreground," "right background"),
the relationship of elements ("to the right of," "above this," "immediately
to the left of"), or colors ("yellow hat," "red wings") can be conveyed
with little difficulty. Such free-text descriptions need not be extensive
and should convey only objective accounts of content. Their most obvious
fault is that they introduce an element of inconsistency, in that the
cataloguer is free to use natural language rather than controlled keywords
or structured strings of terms.
Controlled descriptors,
which are certainly the most popular means of describing visual content,14 consist
of either alphabetically arranged headings or descriptors, such as
the Library of Congress Subject Headings (LCSH), which include
some shallow hierarchical relationships but as a whole are not structured
hierarchically like a thesaurus, or of terms that carry with them hierarchical
relationships. These relationships range from the broad to the specific
(such as ICONCLASS, AAT, and Index of Christian Art subject terms).
Individual headings from
a straightforward alphabetical list might seem to be easier to apply
and easier to retrieve; in reality, greater coverage and more powerful
searching capabilities are possible with a hierarchically structured
system, where more context is given for individual themes or concepts,
and it is possible to relate elements within a broader framework.
Another aspect of
end-user searching, which the other authors of this publication
also mention,
is the fact that elements such as titles or captionsalone or
in combination with the subject matter element and other elements such
as date, style, or periodare frequently employed by end-users
seeking subject access to visual materials. End-user systems
and user interfaces need to take this into account.
Primary-Secondary-Tertiary
Most classification systems attempt to prioritize subject matter, usually on
the three different levels Panofsky called description, identification,
and interpretation. This approach to viewing and recording content
more often than not also reflects the mental approach of the viewer. Even
when there are no corresponding formal divisions in a particular database
structure, it is still advisable to mentally approach content in terms of
such a tripartite division and to classify content in terms of highest to
lowest priority. As a general rule, the cataloguer should regard the primary
level as the overall theme or subject; this is usually a broad type of descriptor
such as "portrait," "seascape," or "still life." From my own experience,
I would recommend that no more than three or four such high-level terms be
used; when more are used, it is nearly impossible for the end-user to understand
what the main subject is without actually seeing the work.
The age-old belief that the main
subject of a work of art is the one that visually predominates does not always
hold true; hence, it is up to the cataloguer to determine what is most significant.
More than anything else, it is the cataloguer who determines what is important
and what should be classified and how. Image quality, when the cataloguer
is working with a reproduction of the work of art, can often significantly
affect cataloguing. Poor-quality images, where details cannot be seen,
can impede the classification process; black-and-white images can prevent
color significance from being included.15 Under ideal circumstances,
cataloguing should proceed only where image quality is good enough for
the cataloguer to see all the details of the work being catalogued. In
practical terms, however, cataloguers usually have to work with the images
available to them; under such circumstances it is advisable to include
as much as possible, even when there is some ambiguity.
Once the primary level descriptors
have been applied, most classification structures offer the opportunity
to classify a combination of generic types, as well as details specific
to that
work of art. An image may be a view of a bridge, but if the particular
bridge can be identified, that fact should be recorded in an orderly and
structured
format. ICONCLASS provides a flexible yet consistent structure within which "named" elements
can be identified. In classifying a bridge in an image, for example, the
final notation (25I1451) is built in a series of stages, each of which
has its own associated keywords.
2 Nature
25 earth, world as celestial body
25I city-view, and landscape with man-made constructions
25I1 city-view in general, 'veduta'
25I14 public road
25I145 canals, waters (in city)
25I1451 bridge in a city across a river
25I (USA, NY, NEW YORK, BROOKLYN) 1451
Underlying this notation are the searchable keywords "nature," "earth," "world," "landscape," "veduta," "city-view," "ideal
city," "public road," "road," "canal," "river," "bridge."
In handling the individual
elements of an image, structure is imperative not only in terms of
data entry but also in terms of retrieval. If terms are controlled, it
is
important that other cataloguers, in a shared environment, be able
to access them to avoid duplication. Standards should be used in formulating
strings of keywords or textual references. Even when it comes to naming
a generic type of object depicted in an image, such as a piece of fruit,
it is important to have well-defined data entry rules: Is the singular
or the plural ("apple" versus "apples" versus "apple(s)") to be used?
Issues such as case sensitivity in searches ("Apples" versus "apples" versus "APPLES")
can be resolved using information technology, but the decisions about
how to handle such policies must be decided in advance by the individuals
who are building those systems and writing the rules for data entry
in them. As we have seen throughout this volume, the use of syndetically
structured vocabularies can overcome differences in the terms used
to describe or search for the same item (for example, "aubergine" versus "eggplant").
Organizing data into significant
groupings is also useful, especially when large bodies of similar material
are being catalogued. Even high-level descriptors can prove invaluable
both for accurate search and retrieval and to enable users to browse
through similar items. For example, American cityscapes could be prefaced
with the International Organization for Standardization (ISO) three-letter
country code USA, French cityscapes with FRA, and so on.16 If
one is using a true thesaurus such as the Getty Thesaurus of Geographic
Names, it is easy to construct hierarchical strings that go from
the nation down through states, counties, and other political subdivisions
to the level of detail desired, until the specific place is named:
FRA, Haute-Normandie, Seine-Maritime
SYR, Damascus
GBR, Oxfordshire, Blenheim Palace
USA, CA, San Francisco
Representations of scenes from different works of literature, operas,
and so on can be similarly structured, as can geographic names such as "Persia" or "Flanders," which
no longer exist as political or administrative entities. All these kinds
of groupings enable speedier and more efficient retrieval, as well as consistency
in cataloguing.
In deciding what structure to use, it is necessary to look at the factors
such as the nature of the material being catalogued, the level of detail
to which cataloguing will be done, the information system that will be
used, and, first and foremost, who the users are who will query the infomation
system and what their needs are.
If the material is diverse in
nature and covers different periods, media, and styles, then the cataloguing
process will clearly take longer than in a narrowly focused image archive
in which similar subject matter predominates. In an image collection with
diverse materials, workflow charts in which different individuals, ideally
each with expertise in a particular area, are assigned particular areas of
responsibility can facilitate the cataloguing process.
The level of detail to which
cataloguing takes place and the experience and skill of the cataloguers
are determining factors in the success or failure of a cataloguing
project. Traditionally, image archives have opted for a fairly minimal
subject
record in which only four or five terms were applied to an image, in
the belief
that these records could be upgraded in the future. Unfortunately,
such improvements rarely take place. The alternative approach has been
to
catalogue images in detail from the outset, which is certainly more
time-consuming but enables greatly enhanced end-user access to the material.
If staffing
and resources permit, I believe that it is advisable to choose the
latter approach and to provide as extensive coverage as possible.
Conclusion
A survey of members of the Art Libraries Society of the United Kingdom
(ARLIS/UK) showed that content classification in art image repositories
is performed chiefly by "librarians," "archivists," or "cataloguers."17 These
people are trained to analyze visual subject matter and to use the appropriate
reference tools, data standards, and vocabularies to describe them. Obviously,
knowledge of the subject or material being classified is highly desirable.
And, as I have stressed in this essay, the ability to work methodically
and consistently is crucial.
To recapitulate, I believe
that high-quality, thorough image cataloguing can be in four main stages:
- Slow down the cataloguer's mental processes
in viewing the work of art, to ensure that it is
being viewed in its entirety and not selectively
- Analyze the work of art in terms of overall subject
matter and select a set of primary descriptive
terms or keywords
- Catalogue the main visual elements, using a systematic
approach to "reading" the work of artleft
to right, right to left, top to bottom
- Determine and catalogue the meanings or symbolism
in the subject matter as time, money, and expertise
permit
It is important to keep in mind at all times what
end-users could possibly want in an image and to
attempt to classify those elements within a reasonable
amount of time.
As long
as a human element is involved in the cataloguing
processsomething that will remain with us for
the foreseeable futurethe role of the cataloguer
is destined to be the most significant in the entire
classification process. It is only by understanding
this crucial aspect of the process that end-user
access to images can be enhanced.
Notes
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