An OWL-based index of emblem metaphors

This paper describes an index on metaphor in Otto Vaenius’
emblem book Amoris divini emblemata (Antwerp, 1615). The
index should be interesting both for its contents (that is, for
the information about the use of metaphor in the book) and
as an example of modelling a complex literary phenomenon.
Modelling a complex phenomenon creates the possibility to
formulate complex queries on the descriptions that are based
on the model. The article describes an application that uses this
possibility. The application user can interrogate the metaphor
data in multiple ways, ranging from canned queries to complex
selections built in the application’s guided query interface.
Unlike other emblem indices, the metaphor index is not meant
to be a tool for resource discovery, a tool that helps emblem
scholars fi nd emblems relevant to their own research. It presents
research output rather than input. The modelling techniques
that it exemplifi es should help a researcher formulate detailed
observations or fi ndings about his research subject – in this
case, metaphor – and make these fi ndings amenable to further
processing. The result is an index, embedded in an overview
or explanation of the data for the reader. I will argue that for
research output data it is up to the researcher who uses these
modelling techniques to integrate the presentation of data in
a narrative or argument, and I describe one possible way of
effecting this integration.
The paper builds on the techniques developed in (Boot 2006).
The emblem book is encoded using TEI; a model of metaphor
(an ontology) is formulated in OWL; the observations about
the occurrence of metaphors are stored as RDF statements.
An essay about the more important metaphors in this book
is encoded in TEI. This creates a complex and interlinked
structure that may be explored in a number of ways. The essay
is hyperlinked to (1) individual emblems, (2) the presentation of
individual metaphors in emblems, (3) searches in the metaphor
data, and (4) concepts in the metaphor ontology. From each of
these locations, further exploration is possible. Besides these
ready-made queries, the application also facilitates user-defi ned
queries on the metaphor data. The queries are formulated
using the SPARQL RDF query language, but the application’s
guided query interface hides the actual syntax from the user.
Metaphor model
There is a number of aspects of metaphor and the texts where
metaphors occur that are modelled in the metaphor index.
A metaphor has a vehicle and a tenor, in the terminology of
Richards (1936). When love, for its strength en endurance
in adversity, is compared to a tree, the tree is the vehicle,
love is the tenor. It is possible to defi ne hierarchies, both
for the comparands (that is, vehicles and tenors) and for the
metaphors: we can state that ‘love as a tree’ (love being fi rmly
rooted) belongs to a wider class of ‘love as a plant’ (love
bearing fruit) metaphors. We can also state that a tree is a
plant, and that it (with roots, fruit, leaves and seeds) belongs
to the vegetal kingdom (Lakoff and Johnson 1980). It often
happens that an emblem contains references to an object
invested with metaphorical meaning elsewhere in the book.
The index can record these references without necessarily
indicating something they are supposed to stand for.
The index can also represent the locations in the emblem (the
text and image fragments) that refer to the vehicles and tenors.
The text fragments are stretches of emblem text, the image
fragments are rectangular regions in the emblem pictures. The
index uses the TEI-encoded text structure in order to relate
occurrences of the comparands to locations in the text.
The metaphor model is formulated using the Web Ontology
Language OWL (McGuinness and Van Harmelen 2004). An
ontology models the kind of objects that exist in a domain,
their relationships and their properties; it provides a shared
understanding of a domain. On a technical level, the ontology
defi nes the vocabulary to be used in the RDF statements in
our model. The ontology thus limits the things one can say;
it provides, in McCarty’s words (McCarty 2005), the ‘explicit,
delimited conception of the world’ that makes meaningful
manipulation possible. The ontology is also what ‘drives’ the
application built for consultation of the metaphor index. See
for similar uses of OWL: (Ciula and Vieira 2007), (Zöllner-
Weber 2005).
The paper describes the classes and the relationships between
them that the OWL model contains. Some of these relationships
are hierarchical (‘trees belong to the vegetal kingdom’), others
represent relations between objects (‘emblem 6 uses the
metaphor of life as a journey’ or ‘metaphor 123 is a metaphor
for justice’). The relationships are what makes it possible to
query objects by their relations to other objects: to ask for all
the metaphors based in an emblem picture, to ask for all of the
metaphors for love, or to combine these criteria.
Application
In order to present the metaphor index to a reader, a web
application has been developed that allows readers to consult
and explore the index. The application is an example of an
ontology-driven application as discussed in (Guarino 1998):
the data model, the application logic and the user interface are
all based on the metaphor ontology.
The application was created using PHP and a MySQL database
backend. RAP, the RDF API for PHP, is used for handling RDF.
RDF and OWL fi les that contain the ontology and occurrences are stored in an RDF model in the database. RDF triples that
represent the structure of the emblem book are created from
the TEI XML fi le that contains the digital text of the emblem
book.
The application has to provide insight into three basic layers of
information: our primary text (the emblems), the database-like
collection of metaphor data, and a secondary text that should
make these three layers into a coherent whole. The application
organizes this in three perspectives: an overview perspective,
an emblem perspective and an ontology perspective. Each of
these perspectives offers one or more views on the data. These
views are (1) a basic selection interface into the metaphor
index; (2) an essay about the use and meaning of metaphor in
this book; (3) a single emblem display; (4) information about
metaphor use in the emblem; and (5) a display of the ontology
defi ned for the metaphor index (built using the OWLDoc).
The paper will discuss the ways in which the user can explore
the metaphor data.
Discussion
The metaphor index is experimental, among other things in
its modelling of metaphor and in its use of OWL and RDF
in a humanities context. If Willard McCarty is right in some
respects all humanities computing is experimental. There is,
however, a certain tension between the experimental nature
of this index and the need to collect a body of material and
create a display application. If the aim is not to support resource
discovery, but solely to provide insight, do we then need this
large amount of data? Is all software meant to be discarded, as
McCarty quotes Perlis? The need to introduce another aspect
of metaphor into the model may confl ict with the need to
create a body of material that it is worthwhile to explore. It
is also true, however, that insight doesn’t come from subtlety
alone. There is no insight without numbers.
McCarty writes about the computer as ‘a rigorously disciplined
means of implementing trial-and-error (…) to help the scholar
refi ne an inevitable mismatch between a representation and
reality (as he or she conceives it) to the point at which the
epistemological yield of the representation has been realized’.
It is true that the computer helps us be rigorous and disciplined,
but perhaps for that very reason the representations that the
computer helps us build may become a burden. Computing can
slow us down. To clarify the conceptual structure of metaphor
as it is used in the book we do not necessarily need a work
of reference. The paper’s concluding paragraphs will address
this tension.
Figure 1 Part of the classes that make up the metaphor ontology.
Arrows point to subclasses. The classes at the bottom level are
just examples; many other could have been shown if more space
were available.For simplicity, this diagram ignores class properties
Figure 2 A metaphor and the properties
relating it to the comparands
Figure 3 Objects can be queried by their relations
Figure 4 Overview perspective Figure 5 Clicking the hyperlink ‘plant life’ (top right)
executes a query with hits shown in the left panel
Figure 6 Emblem perspective with one
metaphor highlighted in picture and text
Figure 7 Ontology perspective , with display of class metaphor
Figure 8 Expert search, start building query
Figure 9 Expert search. Click ‘+’ to create more criteria
Figure 10 Expert search. Select the desired criterion
Figure 11 Expert search. Final state of query Figure 12 Expert search. Display of executed
query and generated RDQL in results panel
References
Antoniou, Grigoris and Van Harmelen, Frank (2004), A
Semantic Web Primer (Cooperative Information Systems;
Cambridge (Ma); London: MIT Press).
Boot, Peter (2006), ‘Decoding emblem semantics’, Literary and
Linguistic Computing, 21 supplement 1, 15-27.
Ciula, Arianna and Vieira, José Miguel (2007), ‘Implementing an
RDF/OWL Ontology on Henry the III Fine Rolls’, paper given
at OWLED 2007, Innsbruck.
Guarino, Nicola (1998), ‘Formal Ontology and Information
Systems’, in Nicola Guarino (ed.), Formal Ontology in
Information Systems. Proceedings of FOIS’98, Trento, Italy, 6-8
June 1998 (Amsterdam: IOS Press), 3-15.
Lakoff, George and Johnson, Mark (1980), Metaphors we live
by (Chicago; London: University of Chicago Press).
McCarty, Willard (2005), Humanities Computing (Basingstoke:
Palgrave Macmillan).
McGuinness, Deborah L. and Van Harmelen, Frank
(2007), ‘OWL Web Ontology Language. Overview. W3C
Recommendation 10 February 2004’, <http://www.w3.org/
TR/owl-features/>, accessed 2007-02-24.
Richards, Ivor Armstrong (1936), The Philosophy of Rhetoric
(New York, London: Oxford University Press).
Zöllner-Weber, Amelie (2005), ‘Formale Repräsentation
und Beschreibung von literarischen Figuren’, Jahrbuch für
Computerphilologie – online, 7.