Exhibition: A Problem for Conceptual Modeling in the Humanities

Contents
1. Introduction
2. Exhibition
3. An Example
4. Why Exhibition is a Problem for Modeling
5. Relevant Work
6. False Resolutions
7. Conclusion
Introduction
There has recently been increased interest within the
humanities computing community in formalizing the
'semantics' of document markup (e.g., Sperberg-McQueen et
al., Buzzetti, Witt, Renear et al. 2002, Bayerl et al., Dubin et
al., Sasaki), or, in an alternative characterization, developing
'conceptual models' that generalize the representation of the
textual structures (Cover). We endorse this agenda, which has
been a long time in the making (Raymond et al.), but we also
wish to draw attention to some difficulties that may be unique
to cultural material.
Natural human communication is characterized by what might
be termed plenary semiosis. Without waiting for formal
languages to be provided humans immediately proceed to
attempt to say everything they think, and, at least arguably,
they generally succeed. The result is that natural communication
systems exhibit every imaginable feature that troubles
knowledge engineers: fuzzy predicates, modal notions,
non-extensional contexts, incompleteness, inconsistency,
ambiguity, and so on. But there is an additional complexity as
well. Human communication takes place within social contexts
that, as linguists and philosophers have been telling us for some
time, confound efforts to conceptualize it as sets of assertions
only. These two aspects of human communication, plenary
semiosis and multiple interacting levels of non-assertional
representation combine to produce some of the most difficult,
and significant, features of communicative artifacts. We
describe one of these features and argue that unless current
conceptual modeling systems are extended to accommodate
this and other related features those systems will be inadequate
for the representation of cultural objects.
Exhibition
I n ordinary linguistic communication we often use a name
to refer to something in order to then go on to attribute some
property to that thing. However when we do this we do not
naturally construe our linguistic behavior as being at the same
time an assertion that the thing in question has that name. We
do however have a particular cognitive relationship to this latter
state-of-affairs; it is just that this attitude is not one of assertion
— we rely on, or are committed to, or presuppose that the thing
in question has the name we are using to refer to it, but we are
not asserting that it does.
We refer to this relationship as exhibition. We say that the brief
document/utterance "Moby Dick was written by Herman
Melville" exhibits the state of affairs that "the name of the
author of Moby Dick is 'Herman Melville'", but it does not
assert that state of affairs. What it does assert is that Melville
is the author of Moby Dick. Although naming is our prototypical
example of exhibition in this paper, we believe that exhibition
is a widespread and diverse phenomenon.
An Example
Consider this XML markup, adapted from the TEI
Guidelines (P4):
<bibl>
<author>Edward R. Tufte</author>
<title>Envisioning Information</title>
<pubPlace>Cheshire, Conn.</pubPlace> <publisher>Graphics Press</publisher>
</bibl>
The Guidelines characterize these element types as follows:
• author: "... contains the name of the author(s), personal or
corporate, of a work ...".
• title: "... contains the title of a work ...".
• publisher: "...provides the name of the organization
responsible for the publication ... of a bibliographic item".
• pubPlace: "contains the name of the place where a
bibliographic item was published."
Close reading of these definitions reveals that these markup
tags convey two quite different sorts of information:
Set A
1. Edward R. Tufte authored Envisioning Information.
2. Envisioning Information was published by Graphics Press.
3. Envisioning Information was published in Cheshire,
Connecticut.
Set B
1. The name of the author of [this book] is "Edward R. Tufte".
2. The name of the publisher of [this book] is "Graphics Press".
3. The name of the place where [this book] was published is
"Cheshire, Connecticut".
Why this is a Problem for Modeling
First, note that the markup is overloaded. The markup tag
author is used to say that something is a name, and it
is also used to say that someone is an author (or the author of
a particular book). Consider a representation in any commonly
used data modeling language, say, RDF's graph-based
representation: nodes for individual entities and arcs for binary
relationships between them. We would expect a single arc for
the assertion represented by a single element — but here
apparently a single element must be unpacked into two arcs.
TEI specialists are fond of saying that TEI markup is about the
text, not about the world the text is about; but we see plainly
this isn't always so. And we also note that this overloading
crosses a profound and famously troublesome semantic
boundary: that between using an expression and mentioning it.
But the most revealing feature of this analysis is that when we
take the union of assertions in sets A and B we will have a
model of possible semantic content that, as a whole, is almost
certainly incorrect; at least in this sense: it is unlikely that there
is any single communicative object whose semantics is correctly
modeled by this set of assertions. There are two cases to
consider; we present them using some terminology ('expression',
'work') from the Functional Requirements for Bibliographic
Records (IFLA 1997) and distinguish two senses of 'XML
document' (Renear et al. 2003).
1. Consider first an XML document that is understood to be
a symbolic expression realizing an intellectual work such
as, say, a manual about web design. Such a document will
be correctly understood as making the assertions in Set A,
but not as asserting any of the assertions in Set B.
2. Now consider an XML document that is a transcription of
a source text, that is, a document that is an expression
realizing a work which is itself a "theory of the text"
(Sperberg-McQueen); that text (expression) being the text
of the manual (a work). Such a document would generally
be understood as making the assertions in Set B, but not as
asserting any of the assertions in Set A.
As a consequence a correct graph model for either case cannot
represent the assertions (as assertions) in the other case.
However a correct representation of Case 1 could represent
Case 2 assertions as exhibitions — if specific expressive
devices, qualified arcs say, were available for this
representation. This is the extension that we are recommending.
Some clarification of these intricacies may be useful. First note
that the cases are not isomorphic: Case 1 asserts the propositions
in Set A and exhibits those in Set B, but Case 2, although
asserting the propositions in Set B, does not exhibit the
propositions in Set A. While might be plausibly argued that the
propositions in Set B logically imply those in Set A, and so any
document that asserts Set B asserts Set A, we would resist this
for two reasons: first because the intuitive logic of assertion
simply does not seem to require that all logical implications of
asserted propositions are themselves asserted; and second
because we suspect that a completely correct presentation of
Set B, one more in line with TEI doctrine on the textual
orientation of markup, would eliminate all commitments to
books, authors, and authorship, and that paraphrase would block
the logical implications in any case. What one could say
however is that in Case 2 the Set A propositions occur in oratio
obliqua.
We also note, as an illustration of the usefulness of the concept
of exhibition, that scholarly transcription into TEI markup can
be understood as identifying exhibitions and then re-expressing
them as assertions.
Relevant Work
The rudiments of this problem have already made an
appearance in the Semantic Web and Dublin Core
communities. However we do not think its significance, at least
for cultural material involving human communication, is fully
appreciated. Dan Brickley, chair of the W3C Semantic Web
Interest Group has noted that the Dublin Core dc:creator element is defined in a way that encourages a similar confusion
between names and things (Brickley), not surprisingly, as the
definition of dc:creator is similar in logical structure to
the ones we cite from the Guidelines:
"Examples of a Creator include a person, an organization,
or a service. Typically, the name of a Creator should be
used to indicate the entity." (DCMES 2003)
The varying usage of the dc:creator code (sometimes for
Creators, sometimes for their names) amongst metadata
encoders is now recognized as a serious practical problem for
the development of an 'abstract model' for Dublin Core.
(Powell).
It is of course in the context of efforts to be absolutely precise
and formal that the problem is acute. Jeremy Carroll, co-editor
of the W3C Recommendation Resource Description Framework
(RDF): Concepts and Abstract Syntax, writes in a posting on
w3c-rdfcore-wg:
I have been looking through the (RDF) primer, particularly
looking at the Dublin Core examples (throughout the primer).
These seem like perfectly fair examples of how Dublin Core
is used. Unfortunately, there are many instances where strings
are used to represent people and things rather than themselves.
This is not in agreement with the model theory...
(Carroll)
Carroll then goes on to note that given the RDF model theory
incorrect implications immediately ensue: in our example for
instance, that Moby Dick was authored by a string rather than
by a person.
False Resolutions
Three deflationary perspectives on this problem are
possible.
One, anticipated from the TEI community, is that TEI encoding
always represents the features of the linguistic text only and
'real-world' assertions are either misunderstandings, mistakes,
or anomalies. This may be so, although we are skeptical as to
whether this stance can be maintained with respect to the full
range of TEI applications. But in any event exhibition remains
a common feature of communicative artifacts, characteristic of
many XML element sets, and of many other systems of
symbolic communication. It must be accommodated.
Another approach, this one anticipated from the Semantic Web
community, is simply to insist on an unambiguous corrected
conceptual representation: one arc for being named "Herman
Melville", one for authoring Moby Dick. But this resolution
fails for the reasons presented in the preceding section.
Although this model would be in some sense an accurate
representation of "how the world is" according to the document,
it would not represent what is asserted by the document. The
authorship arc in the corrected RDF graph model will
correspond to relationships of exhibition, not assertion; and
there is no accommodation for this distinction in the modeling
language.
Finally, it is also natural to feel that the phenomenon of
exhibition is similar in some respects to the already noted much
studied phenomenon of linguistic presupposition and to wonder
whether exhibition is simply a special case of presupposition
(Levinson). Currently we are undecided on this issue but we
note that even if exhibition does turn out to be a form of
presupposition that would remove neither the difficulty
exhibition creates for conceptual modeling, nor its intellectual
significance. In fact it would be a rather substantial finding to
determine the matter one way or the other.
Conclusion
The phenomenon of exhibition is not limited to the simple
naming examples used above. We believe it is
characteristic of communication and communicative cultural
artifacts in general. For instance when we title our articles we
do not say that the title is a title, although we exhibit it as a
title, allowing that inference to be drawn (Renear). Or for a
quite different sort of case: consider how morphological
distinctions exhibit our commitments to syntactical roles,
without actually asserting that the words in question are playing
those roles — though indeed we use those words with those
particular grammatical and syntactical properties in order to
make the assertions we do make.
We conclude that current conceptual modeling projects within
the humanities computing community will fail to be adequate
for the study of cultural objects if they take the approach of the
Semantic Web community and see exhibition as a simple
problem of ambiguity or error, rather than defining new
constructs to express these distinctive relationships. To be
adequate for the humanities, conceptual modeling must be
extended to accommodate the data of the humanities.
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