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Sara Shatford Layne
Head, Cataloging Division, Science and Engineering
Library
University of California, Los Angeles
One of the most important means of enabling users to locate art images
is subject access, but providing such access is a complex and sometimes
messy process. To clarify the issues, I begin by exploring two questions:
What is subject access? What is an art image? During this exploration,
I hope to show how the answers to these questions can affect the ways
in which the subjects of art images are analyzed and access is provided
to them. Then, I look at the steps involved in analyzing subjects and
providing access through them to art images. Finally, I summarize the
decisions that need to be made when providing subject access to art images.
What is
subject access? What is an art image? The answers to
these questions may seem at first to be as simple as
the questions themselves, but they become complex as
one considers them in depth. Let us begin by considering
subject access. Subject access is access to an art
image by means of the subject of that image or, more
precisely, the subject of the work or works of art
that image represents. The questions then become: What
is the subject of a work of art? How should that subject
be described in order to provide access to it?
The Subject of a Work of Art
Perhaps the most obvious aspect of the subject of a work of art is what
that work depicts, what it is of. Looking at Edward Sheriff Curtis's
photograph The Eclipse Dance (fig. 1), one might say that it is of a
dance, of people, and even, although very faintly, of a
solar eclipse. Although it may be obvious, the of aspect of a
work of art is not necessarily simple. People and objects may be the
first kind of of-ness that comes to mind, but a work of art may
also depict activities or events (as, for example, a dance or a solar
eclipse), places, and times. It can be useful to consider these various
kinds of of-ness when thinking about the subject of a work of
art.
Furthermore, what a work of art is of may be described in a variety
of ways. One way is to describe what the work of art is of in generic
terms. In Categories for the Description of Works of Art (CDWA)1,
this way is called Description, a subcategory under
the category Subject Matter. A second way is to give a specific name
to what the work of art
is of-a subcategory called Identification under the category Subject
Matter in CDWA. Any one subject of a work of art can
be described with a range of terms, from the broadly
generic to the highly specific. For
example, we can describe one of the subjects of Curtis's
photograph as "dance" or
less broadly as "ceremonial dance," and we can also identify it specifically
as "Eclipse Dance." We see "people" who can be identified as "Native
Americans" (or, in Canada, "First Nations") but who can also be identified
more specifically as "Kwakuitl," and, if information were available,
could be still more specifically identified by their
personal names. As we can see, the range from generic
to specific, from description to
identification, can be more of a continuum than a dichotomy.
As another
example, the subject of Frederick Henry Evans's photograph Across
the West End of Nave, Wells Cathedral (fig. 2)
could be described using terms such as "architecture," "religious
buildings," "cathedrals," and "Wells Cathedral." Describing
or identifying a particular subject at just one point
in this range of terms will not necessarily meet the
needs of all searchers for an image. One can easily
imagine a set of circumstances in which describing
the subject of this last image as "religious buildings" would
best meet one searcher's needs, but a different set
in which describing the subject as "cathedrals" would
meet another searcher's needs. And, of course, one
can imagine a third searcher who would best be served
by identifying the subject as "Wells Cathedral."
Although any subject, whether
of a text or an image, can be described in both broad and narrow terms,
images are different from text in that they are always of a specific
instance of something. Unlike a text about religious buildings, an image
cannot be a purely generic depiction of "religious buildings." An image
must necessarily be, if not of a particular known and named building,
at least of a particular type of building or construction. It may be
a church or a monastery, a nave or a cloister, but it must be something
more specific than "religious buildings." This characteristic of images
makes it particularly important to provide access to a subject of an
image at as many points as possible within the range of terms that can
describe or identify that subject.
The three
subjects I have just mentioned—"Eclipse Dance," "Kwakuitl," and "Wells
Cathedral"—show that activities or events, persons,
and objects can be described using a continuum of terms
from the broadly generic to the relatively specific.
It is useful to recognize that place and time can also
be described in generic terms or identified with specific
terms. For time, the difference between generic and
specific is between description of cyclical time and
identification of a chronological time, while for place
it is the difference between description of a kind
of space and identification of a geographic place.
The place of Evans's photograph is the town of "Wells," in
the county "Avon," in the country "England." Speaking
descriptively or generically, the place of the photograph
is "interior." The time of Curtis's photograph is "1910–1914" it
is also "daytime." If we knew more about the photograph
we might be able to identify the season; it might be,
for example, "spring" or "summer." It is easy to imagine
circumstances in which a user would be interested in
a generic description of a place depicted (for example,
interiors of churches) or the identification of a particular
place (for example, churches in England) or a combination
of the two (interiors of churches in England).
Why is it useful to think about
the different kinds of of-ness? It is useful because
it gives us a checklist of the kinds of subject—persons,
objects, activities, places, times—to consider
when describing or assigning subject terms to art images.
Thinking about
the ways in which any single subject may be described
or identified within a range of generic and specific
terms gives us another checklist to use when identifying
possible subjects; it may also affect the very structure
of the information system providing user access.
For example, it seems reasonable to assume that any
image of "Wells Cathedral" is also an image of "cathedrals," an
image of "religious buildings," and an image of "architecture." Rather
than having to assign each of these terms to each
image of Wells Cathedral, would it not be preferable
to assign just the specific identifying term and
have a system that inferred the generic descriptive
terms from the specific identification? This is what
the ICONCLASS system does in assigning higher-level
terms for a specific description, as discussed by
Colum Hourihane in his essay in this volume. But
a local authority file could also be designed to
carry the broader or more generic descriptive terms
each time a specific term or set of terms is applied.
Patricia Harpring discusses the creation of a subject
authority in her essay in this volume.
Less
obvious than the of-ness of a work of art,
but often more intriguing, is what the work of art
is about, which corresponds to the subcategory
Interpretation under Subject Matter in CDWA. Sometimes
the about-ness of a work of art is relatively
clear, as in Georg Pencz's Allegory of Justice (fig.
3). This image is of a naked woman holding
a sword and scales, but the title tells us that the
image is an allegorical figure representing justice
or, in other words, that the image is about the
abstract concept "justice." In Goya's drawing Contemptuous
of the Insults (fig. 4), the about-ness is
slightly less obvious, but it is still clear that
this work of art has some meaning beyond simply what
it is of. Indeed, a description of what it
is of—a man, perhaps Goya himself, gesturing
toward two dwarfs wearing uniforms—is not really
sufficient to make sense of this image; it symbolizes
something else, it is about something else:
the relationship between Spain and France at the
beginning of the nineteenth century or, more specifically,
Goya's personal attitude toward the French occupation
of Spain.
Let us look at a few more examples
of ways in which both of-ness and about-ness are
present in an art image. In a death scene by Gerard
Horenbout (pl. 1) in a sixteenth-century Flemish
book of hours, one part of the image depicts a person
dying, while another part shows a decaying corpse
on horseback, which symbolizes death. One could say
that this work of art is both of death (the
man in the bed is experiencing death) and about death
(the corpse). In fact, this image is really about death
in two different senses: the figure of the corpse
personifies or symbolizes death, but the entire image
or combination of scenes is about the omnipresence
and inescapability of death.
The
Destruction of Jerusalem (pl. 2) by the fifteenth-century
Boucicaut Master reveals yet another kind of about-ness.
In this image, which ostensibly depicts the siege
of Jerusalem by the Romans in the first century,
we see a somewhat stylized representation of
a fifteenth-century French city, not a realistic
depiction of first-century
Jerusalem. Similarly, the people in the manuscript
illumination appear to be fifteenth-century French
people, not Romans from the first century or
the
civilian inhabitants of first-century Jerusalem.
One could say that this work of art is of a
fifteenth-century French city and of fifteenth-century
French people, but it is about first-century
Jerusalem and its inhabitants, about the
Roman emperor Titus and his soldiers. Both the of-ness and
the about-ness of this work of art could
be of interest to users. It could be of interest
to
one researcher because of its depiction of a
fifteenth-century city and to another because
it is about Jerusalem.
To still a third researcher, interested perhaps
in what the scenery for a medieval European mystery
play might have looked like, the fact that it
depicts a fifteenth-century city as a representation
of
first-century
Jerusalem would in itself be valuable.
The
Birth of Esau and Jacob by the fourteenth-century
Master of Jean de Mandeville (fig. 5) is similar
to the previous example. This image depicts fourteenth-century
European people, clothing, furnishings, and childbirth
customs, but it is intended to represent an event
that would have occurred several thousand years
earlier on a different continent. In other words,
it is of babies
and midwives and baths and beds in medieval Europe,
but it is about the biblical Esau and
Jacob and their mother Rebecca.
In
these last five examples, the works of art were,
one might
say, designed or intended as allegories or symbolic
expressions, and their about-ness can
perhaps be seen as an essential element of their
subject
analysis. But there are other works of art in
which about-ness may
be more tenuous, less clear, and perhaps even
an unnecessary element of subject analysis. Consider
the photographs by Evans and Curtis. Are these
works of art about anything? Whether they
are perceived as about something, and
what they are perceived as being about,
may depend to a great extent on the background
of the person beholding the work of art. Is Evans's
photograph about peace or timelessness
or oppressive severity? Is Curtis's photograph about superstition
or respect for nature? Is it about the
human impulse to explain and control natural
phenomena? When determination of about-ness requires
highly subjective judgment, should that determination
be included in providing subject access to art
images? Should the inclusion of about-ness in
subject analysis be limited to works of art that
are clearly allegorical or symbolic in nature?
These questions need to be considered when providing
subject access to art images.
Why
is it useful to identify the ways in which a work
of art can be of or about a particular
subject? It is useful because it leads us to consider
the various aspects of the subject of a work of art,
to which aspects it is worth providing access, and
whether it is necessary to make distinctions between
and among these various aspects. Is it necessary
or useful to make a distinction between an image
that is about death and one that is of death?
Is it appropriate to provide access to about-ness that
is highly subjective? If such access is provided,
is it necessary or useful to make a distinction between
an image that contains an allegorical or symbolic
personification of death or justice and one
that is about death or justice in a more subjective
sense? Is it necessary or useful to make a distinction
between historically accurate representations of Jerusalem
and representations that are better described as
being about Jerusalem? These questions also
need to be considered when providing subject access
to art images.
Some images, such as Horenbout's Death Scene,
the Boucicaut Master's The Destruction of Jerusalem,
and the Master of Jean de Mandeville's The Birth
of Esau and Jacob, accompany, illustrate, or
are in some way about literary works. Death Scene accompanies
the Office of the Dead2, The Destruction
of Jerusalem appears in the manuscript Des
cas des nobles hommes et femmes3,
and The Birth of Esau and Jacob prefaces the
portion of the biblical Book of Genesis that describes
that event. These literary works can be seen as another
kind of description of the subject of the
work of art, and therefore access to art images through
the names of literary works may be considered, when
appropriate, as providing an additional form of subject
access.4
Although
I am focusing on subject access to art images in
this essay, I think it is useful to discuss briefly
a category of access that is not, strictly speaking,
subject access but is sometimes thought of in conjunction
with, or even overlaps, subject access. This category
of access, called Object/Work-Type in CDWA, describes
not what the work of art is of or about but
the kind of work that it is. The category
Object/Work-Type can overlap with Subject for two
reasons. The first is that, in some cases, the subject
matter of an image can also be its Object/Work-Type.
For example, "landscape" describes subject matter
in the painting Mythological Scene by Dosso
Dossi (pl. 3), although this image is, however, not
a "landscape" in the Object/Work-Type sense. A painting
from, say, the Barbizon School (a group of mid-nineteenth-century
landscape painters) is both "a landscape" in the
Object/Work-Type sense and depicts a "landscape" in
the Subject sense.
The
second reason that Object/Work-Type can overlap Subject
is that, in the case of one work of art being depicted
in another work, the term used to describe the Object/Work-Type
of the depicted work becomes the term used to describe
a Subject of the work in which it is depicted. In
Evans's photograph of Wells Cathedral, "cathedral" is
an Object/Work-Type of the depicted building, but
since the photograph is of a cathedral, "cathedral" becomes
a Subject of the photograph, not its Object/Work-Type;
the Object/Work-Type of the artwork in hand is "photograph." Or,
one might have an etching that depicts an artist
at work in his studio surrounded by his paintings.
Such an image would have "etching" as its Object/Work-Type,
but "paintings" as a Subject. One searcher may want
images that depict paintings; another searcher
may want artworks that are paintings. Failing
to distinguish between artworks that are paintings
and artworks that depict (that is, are of)
paintings diminishes the potential for precision
in retrieval: searchers looking for just those images
that are of paintings or just those artworks
that are paintings will not be able to specify
or retrieve only those images they want.
What Is an Art Image?
The foregoing discussion of works of art depicted
in other works of art returns us to the big question:
What is an art image? An art image may be a
work of art; it may be an image of a work of art;
or it may be both a work of art and an image
of a work of art.5 Pencz's Allegory
of Justice represents an image—a drawing—that
is a work of art; Sarcophagus with Lid (fig.
6) is an image—a photograph—of a work of
art—in this case, a marble sarcophagus. The
image itself—the photograph—is not a work
of art, although it depicts a work of art—the
sarcophagus. The image that is Evans's photograph Across
the West End of Nave, Wells Cathedral is itself a
work of art and in addition depicts the work
of art that is Wells Cathedral. It is both a work
of art and an image of a work of art. Curtis's
photograph The Eclipse Dance is itself a work
of art, but it is also an image of masks that can
be considered to be works of art in their own right.
Although the details of the masks cannot be seen
in this image, the image does give useful information
regarding these masks, as it shows them in the context
of their use. An image that gives context to a work
of art can be as valuable as an image that depicts
the work more clearly—such as a photograph of
a mask in a museum's collection that shows every
detail precisely—but lacks context.
Why is it important
to note that an art image may be not only a work
of art itself but also an image of another work of
art? First, the name of a given work of art (for
example, Wells Cathedral) or a term that describes
the type of work (for example, "masks") may become,
as we have seen, subject terms when that work is
depicted or represented in another work of art. It
can be useful to consider whether one wishes to distinguish
between artworks that are depicted in other artworks
and those same artworks depicted in images that are
not themselves generally regarded as works of art.
For example, in providing access to images of Wells
Cathedral, would one wish to try to distinguish between
Evans's "artistic" photograph and photographs taken
merely to document what the cathedral looks like?
It seems doubtful that one would wish to make this
distinction, although one would, of course, wish
to provide access to Evans's photograph itself as
a work of art. And if one does not wish to make this
distinction, then the terminology and format of the
access provided should be the same, whether the image
that represents the work of art in question is simply
recording that work or is a work of art in itself.
The
situation in which a single term can describe Object/Work-Type
in one context and Subject in another context can
be generalized as follows: the same term can, in
certain circumstances, describe or identify different
aspects of works of art. For instance, "Goya" can
identify a specific subject of a work of art, and "Goya" can
also identify the creator of a work of art. In the
case of Contemptuous of the Insults, "Goya" is
both Subject and Creator of the work of art. One
can easily imagine that a person seeking images of Goya
would like to have them separated from works of art
created by Goya; however, someone seeking
works by Goya might be very pleased to be
made aware of images that are of Goya. The
point is that it may be useful to employ the same
vocabulary to describe a person or object, whatever
the role of that person or object vis-à-vis
the art image may be, but it is at the same time
necessary to provide a means for organizing such
a retrieval based on metadata elements or categories
of access.6 Using consistent vocabulary
promotes recall of relevant images; providing the
means for organizing the retrieval based on category
promotes precision. Categories can be differentiated
from one another by placing them in different fields
in a database record or otherwise identifying them
as different metadata elements.
A second
reason for pointing out that an art image may contain
representations of works within works is that it
may be desirable to provide subject access to each
separate work of art represented by a single image
and to associate the subject access for a particular
work with just that work–not with a work that
it represents or in which it is represented. Consider Sarcophagus
with Lid. The sarcophagus can be considered the
Subject of the photograph, but it is also the Object/Work-Type
of the work of art represented. Depicted in the photograph
is the side of the sarcophagus that represents an
event from the Trojan War: Hektor's body being dragged
behind Achilles' chariot. But the sarcophagus is
decorated with subjects not shown in this particular
photograph, so that "Odysseus," depicted on an unshown
end, is a Subject of the sarcophagus but not of this
specific image of it. It may be desirable to provide
access to all the subjects of the sarcophagus, while
making it clear which of these subjects is actually
depicted in this particular image of the sarcophagus.
The desire to provide thorough access to the subjects
of a work of art, yet identifying which subjects
are actually depicted in a given image of that work
of art, can influence the choice of a structure or
metadata schema for providing subject access to art
images. The VRA Core Categories, Version 3.0,
provides a category-Record Type-that "identifies
the record as being either a Work record, for the
physical or created object, or an Image record, for
the visual surrogates of such objects."7 Identifying
records in this way could make it possible to distinguish
between the subjects of a work of art and the subjects
of an image of that work.
Providing Subject Access to Art Images
Next I discuss the four steps necessary to provide
access to art images through these subjects. Although
these steps are listed separately and sequentially,
they are not independent of one another or even performed
in the order listed here. Choices made in one step
influence the choices made in another. In the first
step, decisions are to be made regarding which of
the subject aspects discussed above should be used
in providing access to the art images, whether and
which distinctions will be made between and among
these various aspects, and what the depth of the
subject analysis should be. In the second step, someone
or something must be identified to provide the analysis
of the subjects of the image. In the third step,
vocabulary and a metadata structure or format for
recording that analysis must be selected. In the
fourth step, an information system must be chosen
or developed for providing access to the subjects
that have been analyzed and recorded.
Subject Aspect Decisions
How does one decide which subject aspects of art images should be used to provide
access to them? Although available resources are always a factor in such a
decision, the major factor should be what kinds of access are most useful.
Unfortunately, it is very difficult to design research to assess accurately
the usefulness of different kinds of access. Usefulness will inevitably depend
on who needs the access, as well as on the nature of the art image.
Some researchers have analyzed queries made of large
picture or stock-shot files, queries made chiefly
in support of illustration or commerce.8 The
items were not, for the most part, art images, and
the purpose of the queries was generally not the
support of research. The results showed that the
queries tended to be satisfied by an analysis of
what an image is of, not by what an image
is about. My research suggests, however, that about-ness is
a determinant of relevance of art images in approximately
20 percent of art history research.9 This means that
approximately 20 percent of art history research
might benefit from providing access by what a work
of art is about.
I also
found that of-ness was a determinant of relevance
of art images in approximately 35 percent of art
history research, suggesting that providing access
by the of-ness of an art image would be even
more useful than providing access by its about-ness.
In addition, Lucinda Keister suggested, because about-ness is
subjective and someone interested in the about-ness of
an image can generally specify certain of-ness subjects
that it should contain, it is more useful to provide
access by the of-ness of the image. Then the
researcher can browse through a retrieved group of
images and make his or her own determination of about-ness.10 In
support of the position that about-ness can
be at least partly defined by of-ness, Layne's
analysis of research in art history suggests that
in approximately half the cases in which about-ness was
a determinant of relevance, of-ness was also
a determinant.11It might be possible to
choose to index the about-ness of art images
that are clearly personifications or symbols, as
for example "justice" for Pencz's Allegory of
Justice, "Spain-Relations-France" for Goya's Contemptuous
of the Insults, "death" for Horenbout's Death
Scene, and "Jerusalem" for The Destruction
of Jerusalem, but not to index it for more tenuous
and subjective instances, such as Curtis's The
Eclipse Dance.
With
regard to the usefulness of another form of subject
access discussed earlier, namely, the literary work
that an image is about, Layne's analysis of
research in art history suggests that such literary
works are determinants of relevance for approximately
15 percent of art history research. This relatively
small percentage may be more an indication of the
percentage of works of art that are about literary
works than an indication that it is of limited usefulness
when providing access. Indeed, I would say that whenever
a work of art is about a literary work, it would
be useful to provide access through the name of that
literary work.12
Once
it has been decided to index different kinds of subjects,
as for example of-ness and about-ness,
how does one decide whether the distinctions between
or among these different kinds should be preserved
and codified for use in providing access? The disadvantage
of codifying distinctions is that a considerable
amount of time and effort would be required, and
different people can come to different conclusions
about borderline cases. For example, is The Birth
of Esau and Jacob an image of "childbirth," interpreting "childbirth" broadly
as the activities that surround that event, or is it
really about "childbirth," since the actual
emergence of a child into this world is not depicted?
Yet, there are advantages to codifying distinctions.
As mentioned earlier in a slightly different context,
codifying distinctions increases precision in retrieval,
as it makes it possible to retrieve, for example, just
those images that are of "death" and to exclude
those images that are about "death." It also
permits the subdivision of large sets of retrieved
images based on these distinctions. For example, a
search on "death" as a subject could result in a retrieval
of images subdivided into groups based on whether the
image explicitly depicts "death" or is about the theme
of "death."
There
is still a decision to be made with respect to the
depth of subject analysis. Some images, for example The
Destruction of Jerusalem and Death Scene,
are particularly rich in the number of people, objects,
and activities depicted. Other images, such as The Eclipse
Dance, may show people, objects, and activities,
but not very distinctly or clearly. In images such
as these, does one provide subject access to every
single person, object, and activity depicted? Stated
another way, how does one make decisions regarding
the depth of indexing? An image indexing project for
the Bibliothèque Nationale in Paris, now more
than twenty years old, developed guidelines that still
seem valid today: index anything that is clearly depicted;
also index anything that is not clearly depicted if
the mere fact of its presence in the image is informative;
do not index parts of a whole if the whole is indexed
and the parts are implicit in it.13
Let us
look at how these recommendations regarding depth of
indexing might affect the subject analysis of a couple
of art images. For Allegory of Justice, it might
mean that "naked woman" would be indexed, as well as "sword" and "scales," but
not "face" or "breast" or "arm" or "leg," as those
body parts are implicit in "naked woman." For The
Eclipse Dance, it might mean that "masks" would
be indexed, although they are not distinctly depicted,
as their mere presence in the image is of interest.
The goals or focus of a particular institution can
also affect depth of indexing. An institution focusing
on architecture might, for example, want to provide
more detailed indexing for Evans's Across the West
End of Nave, Wells Cathedral, than would an institution
focusing on the history of photography.
It may
not, however, be necessary or even desirable to index
at a level of detail that narrows retrieval to a very
few images. Browsing through a set of possibly relevant
images may be a better way for a searcher to identify
desired images than a highly specific search.14 For
the art historian, for whom comparison is an essential
method of research,15 providing a larger
set of possibly relevant images may lead to connections
and comparisons that otherwise might not have been
made. In addition, practical factors—including
time, money, and the knowledge and skills of the staff
performing the subject analysis—affect the depth
of subject indexing possible for a particular collection.
Performance of Subject Analysis
Who or what performs the analysis of the subject in a work of art? For some
years there has been strong interest in automated analysis of images, and
there have been various attempts to use pattern recognition techniques and
iterative methods to identify and retrieve relevant images. To date, none
of these efforts has been particularly successful in retrieving images from
heterogeneous groups or in identifying objects, such as horses, that can
be depicted in a variety of poses, from many different angles, and under
various lighting conditions.16 Automated systems are most successful
in analyzing homogeneous sets of images and in selecting images based purely
on color, composition, and texture. Such elements are relatively easy to
codify and therefore relatively easy for a computer to identify.17 With
what appears to be significant effort, some systems have had some success
in identifying image types such as landscapes that tend to have certain common
compositional and color characteristics.18 But it is safe to say
that content-based—that is, automated—image retrieval is still
far from being even remotely useful to art historians or art researchers.
A key to the possibly intractable
problems involved in attempting to substitute computer analysis for human
analysis may be found in an unlikely source: an article
by the neurologist Oliver Sacks
concerning the problems encountered by a man, blind almost from birth, whose
physical ability to see was restored to him when he was middle-aged.19 This
man was unable to "see" properly, unable to distinguish, for example, his
black-and-white dog from his black-and-white cat. Sacks postulates that this
difficulty occurred
because the process by which humans learn to interpret what their eyes see
is a complex one that takes place as the brain develops during childhood
and involves senses other than sight.
Subject analysis by humans is
expensive and time-consuming, however, and studies have suggested that
human indexers are not necessarily consistent in
their analysis of subjects.20 There
are, however, various methods by which consistency among humans can be
promoted, including the use of controlled vocabularies,
guidelines for subject analysis,
and even checklists or picklists of possible subject aspects. The ideal
at this time would seem to be to let humans do what
they do best and to let computers
do what they do best. In other words, let humans identify the subjects
of an art image and let computers identify color,
shape, and composition. For example,
if human indexers were to identify the subjects of art images, a computer
could, if desired, then analyze a large retrieved
set of images with the same subject (for example, "cathedrals," "dance," "sarcophagi")
for similarities in shape, color, or composition.21
Choice of Vocabularies and
Format
To provide efficient, accurate subject access to images, vocabularies and a
metadata format must be selected, and decisions must be made regarding the
depth of the subject analysis.
The generally acknowledged advantages
of controlled vocabularies have been discussed elsewhere,22 and the specific
vocabularies that may be most appropriate for subject access to art images
are discussed in the other essays in this publication. There are, however,
three aspects of subject access that are particularly important to vocabulary
choice for art images and should be kept in mind when deciding on vocabularies
for providing access to art images. The first aspect, discussed earlier, is
that an image of something is always of a particular instance of that
something (for example, "Wells Cathedral"), although it may be sought because
it is an image of something that can be described more broadly or
generically (for example, "religious architecture" or "cathedrals"). Regarding
vocabulary choice, this means that to avoid indexing each subject of each
image with every
possible broader term for that subject, it is important to have a vocabulary
with a syndetic structure that provides good links from the broadest to the
narrowest terms, links that lead from the generic to the specific. This is
why thesauri, which have an explicit syndetic structure, are increasingly
popular in projects that attempt to provide good user access to visual materials.
The second aspect of vocabulary
choice for art images is that any given image may be of interest to different
disciplines with different vocabularies. For example, The Birth of Esau
and Jacob might be of interest to historians of medicine who might
wish to use a medical vocabulary, rather than a more general vocabulary,
when
searching for images. Clearly, it is not practical to use all possible
vocabularies when
providing subject access to art images, but if it is known or intended
that a particular collection of art images will be used by a particular
discipline,
it may be worth considering the use of a specialized vocabulary in addition
to a general vocabulary. For example, an image of tulips might be indexed
as "tulips" or
even "flowers" for general users, but scientific species names such as Tulipa
turkestanica might be used as indexing terms if botanists are among
the intended users.
The third crucial aspect of
vocabulary choice for art images is, as discussed earlier, that the same
term can describe
or identify different metadata categories or access points for works
of art. "Goya," for
example, can identify a Creator or a Subject of a work of art or, in
some cases, both. The terms “painting” or “landscape” can
describe an Object/Work-Type or a Subject of a work of art or, in some
cases, both. The terms "painting" or "landscape" can
describe an Object/Work-Type or a Subject, as we
have seen above. If different vocabularies are chosen
for each metadata category, the terms could be slightly
different, depending on the category of access, and
this may not be desirable. So in choosing a vocabulary
for subject access it is important to coordinate
this selection with the choices of vocabulary for
other categories of access in the same information
system.
The advantages and disadvantages
of various formats for describing art images are discussed elsewhere
in this book, as are specific vocabularies and classification systems.
There are, however, two previously discussed aspects of the subjects
of art images that affect the choice of format for providing access
to these subjects. The first aspect is that different
kinds of subjects
may exist in an image, which means that there is the possibility of
distinguishing among them. If there is a desire to
distinguish, for example, between
subjects that describe the about-ness of an art image and those
that describe or identify its of-ness, then the chosen format
needs to support that distinction. The second aspect is that a single
image may represent more than one work of art. In this situation there
may be a need to associate subjects with the appropriate work of art,
and the format used to describe the art image would have to make this
association possible. As mentioned earlier, the VRA Core Categories permits
the distinction between work and image. Conceivably,
this distinction could be used to associate one set of subjects with,
for
example, Wells Cathedral, and another set of subjects with Evans's
photograph of that cathedral.
Choice and Design of a System
The fourth step is the selection or design of an
information system for retrieving and displaying
art images. What I mean here by "information system" is
software that stores, indexes, retrieves, and displays records, and
ideally, the images
that these records describe.
What should a good information
system do with respect to subject access to art images? It should take
thorough advantage of the syndetic structure of vocabularies
to permit retrieval at
varying levels or degrees of specificity and to promote refinement of searches,
broadening or narrowing them as a searcher may require. A searcher looking
for images of "dances" should be able to retrieve the image The Eclipse
Dance and should also be able to refine the search so that it is limited
to images of "ceremonial dances." A searcher looking for images of Wells Cathedral
should be able to refine the search, broadening it to include "cathedrals" or "cathedrals
in England."
A good information system should
be able to take advantage of distinctions among kinds of subjects and
between subject and other categories of access, always
assuming that these distinctions
are present in the metadata schema or format that has been chosen to
describe the images, but ideally without forcing
the searcher to be aware of these distinctions in
advance. Although the information system should recognize
the distinction between the Creator and Subject categories
of access, or between Subject and Object/Work-Type,
it should permit the searcher who has employed a
search term common to both categories to be made
aware of that term's use in both categories while
still preserving the distinction between the categories.
For example, consider a menu-based information system
in which the user of the system is given a list of
categories of access from which to choose, categories
such as Title, Object/Work-Type, and Subject. In
such a system it might be more useful to provide
the user with the selection "Persons" (which would
include persons as subjects, as well as creators)
rather than "Creators." Once the search is performed,
the results could be grouped by the role the person
had vis-à-vis a particular work of art: creator,
subject, owner, and so on. In a system offering a
search on "Persons," a search on "Goya" would retrieve
both works by Goya and works of which he was a subject,
but the results of the search would be presented
as two separate groups, enabling the searcher to
select either group or both. In a system offering
instead Creator and Subject as separate choices,
the searcher must first decide into which category "Goya" fits,
and if Creator is chosen, the searcher may remain
unaware of images of which "Goya" is a subject.
Regarding the display of
images retrieved by a search, a good system should make it possible to
view several images at the same time and to browse among retrieved sets
of images. Ideally, the searcher should be able to rearrange retrieved
images to enhance comparisons among images. As I mentioned earlier, comparison
is an essential element of art history research. Ideally, the searcher
should also be able to refine or reorganize retrieved images based on
characteristics other than subject, and analyses of some of these characteristics,
in particular color, composition, and texture, could be performed by
the system itself at the time of need.
Conclusion
Let us review, in the form of questions to be answered,
the decisions to be made when providing subject access
to art images.
- Having considered the various kinds of subjects—of,
about (or levels of description, identification,
and interpretation), and literary works that an art
image can be about—through which of
them will you provide access?
- If you are providing access to more than one
kind of subject, do you want to codify the distinctions
between or among them?
- What level of analysis, or what depth of indexing,
do you want to provide?
- What vocabularies will you use to record your
subject analysis?
- What metadata schema or format will you use to
describe art images?
- What type of information system will you use
to retrieve and display the art images?
I hope that this essay, together with the others
in this volume, provides the conceptual framework
and information necessary to answer these questions
in ways that improve subject access to art images.
Notes
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