\section{The Warburg Electronic Library Project}
\label{Sec:Warburg}

The Warburg Electronic Library Project (WEL) began within the framework
of an interdisciplinary cooperation \cite{MNS96} between our group and the Art
History department at the University of Hamburg. The goal of this
cooperation is the examination, development and application of digital
libraries for art history research purposes.

The development of this particular digital library focusses on two 
topics:
\begin{itemize}
\item understanding the special requirements of the application 
domain and their adequate realization;
\item personalization of a working environment for art history 
research by tailoring personal digital reference libraries to 
the needs of individual information consumers and specific tasks.
\end{itemize}

\subsection{The Application Domain} 

The application domain of art history is dominated by image material
augmented by texts and multi-media artifacts such as films and audio 
documents. Art history research stresses the examination 
of themes, the identification of represented icons (symbols), events 
and persons and their classification according to these issues.
In the handling of image material automatic image processing  
plays only a subordinate role. Most of the information has to be 
added by people in a value adding process. 

This style of image handling is not restricted to art history. 
Other areas such as marketing and press archives are also primarily 
interested in themes and messages transported by their artifacts 
as well as the represented objects and persons. 


\subsubsection*{The PI-Index}

\e{Political Iconography} (PI) is the
area of art history which examines political messages conveyed in 
images showing regents, politicians, ceremonies, political acts, etc. 
The underlying assumption of the PI is that the effects of
political actions are not restricted to contracts and
political documents but are also depicted in paintings, 
monuments and buildings. 


The art history department has developed an elaborated 
ontology for the classification of images according 
to their political messages called the \e{PI-Index}. This 
ontology consists of a  hierarchy of terms referring  
to politics, political acts, and  social phenomena. 
It includes terms as varying as science, marriage, 
democracy, shepherd, and revolution. 

The classification of image material according 
to this ontology cannot be done automatically. It is itself 
a result of scientific work in the area of art history.
About 250,000 cards with photographs of paintings, etc.
showing politicians, political acts 
and ceremonies, battles and social events from all epochs 
and countries are already classified according to this scheme. 
The classification is not disjoint, many cards are assigned to 
several terms of the index.  


\subsection{Tokens and Artifacts in the Warburg Electronic Library}

Photographs or prints of paintings showing regents 
or related matters, associated texts, speeches of politicians, 
and documentary films about regents like Napoleon, form the relevant 
information tokens in this digital library. The 
tokens are created and included into the information universe 
through scanning or an equivalent digitalization process. A further 
source of tokens is text editing. Scanned image tokens are stored 
as bit vectors in formats like JPEG or GIF. In Tycoon types are associated to these bit vectors and routines, preventing the erroneous use of bit vectors and routines. The following example shows the association of a type \p{T} and the routines \p{scan} and \p{display} for JPEG images:

\begin{xple}
\k{let} jpeg =
\k{tuple}
  \k{Let} T = \dots
  \k{let} scan = bind(:\k{Fun}() :T  "imageLib" "scan\_jpeg\_image")
  \k{let} display = bind(:\k{Fun}(:T) :\k{Ok}  "imageLib" "display\_jpeg\_image")
\k{end}
\k{let} jpegImage = jpeg.scan()
jpeg.display(jpegImage)
\end{xple}
As mentioned in section~\ref{Sec:Framework} the \p{bind} function in Tycoon is used to 
include  external, machine-dependent routines \p{scan\_jpeg\_image} and \p{display\_jpeg\_image} that work on JPEG files.

On this level the tracing environment may provide information 
about the date of digitalization and the identification of 
the person creating this token. 

\begin{figure}[bt] 
\begin{center} 
\leavevmode
\epsfxsize=14cm 
\epsffile{Pictures/abb1.ps} 
\end{center} 
\caption{Napoleon crossing the Alpes at St. Bernhard} 
\label{napo} 
\end{figure}

The tokens are taken as starting points for the artifact 
construction. The image token showing Napoleon crossing the Alps, for 
example, is taken as a basis for an artifact as illustrated in figure~\ref{napo}. The artifact contains a reference to the scanned painting (image token)
and a thumbnail copy of it, as well as information about the artist, the title, and the date of the the painting as well as the location where the original painting can be found and the source of the scanned print of the painting. 

In addition, the artifact is accompanied by content-descriptive 
metadata: It is classified according to the ontology of the  \e{PI-Index} 
and the regent pictured by the token, here Napoleon, is specified. 
This additional information  can be considered as information tokens from a private information source. 

The type representation of this artifact in Tycoon looks as follows:
\begin{xple}
\k{Let} PIArtifact =
\k{Tuple}
  originalImage :Reference(jpeg.T)
  thumbnailImage :jpeg.T
  title :String
  date :Date
  \dots
\k{end}
\end{xple}

\p{Reference} is a data type which abstracts from the distinct kinds 
of possible bindings like external/internal, local/remote etc. 

The Warburg Electronic Library maintains a large 
collection of these artifacts together with services for their 
persistent storage, transmission, retrieval, and presentation. 
On the language level retrieved artifacts may be included into a 
list of type \p{list.T(PIArtifact)} and the associated thumbnail 
images may be displayed by using iteration abstraction provided 
as generic services by a Tycoon library.
\begin{xple}
list.forEach(artifactSelection  \k{fun}(a :PIArtifact) jpeg.display(a.thumbnailImage))
\end{xple}

The library is augmented by an Oracle database containing historical
data on regents of all centuries. The Tycoon SQL-gateway to Oracle 
databases is described in section~\ref{Sec:Framework}. Looking 
up historical data about Napoleon is accomplished by the following 
function of the SQL interface. 

\begin{xple}
oracleSQL.lookup(regents "Napoleon")
\end{xple} 


In addition to image artifacts and structured data the Warburg Electronic Library also contains text collections, e.g. about political iconography and 
political events. These collections can be searched by an Inquery information retrieval engine. Employing the Tycoon Inquery gateway the collection can be searched in the same language framework as the Oracle database. 
\begin{xple}
inquery.eval(politicalEvents "Anything about Napoleon and Waterloo")
\end{xple} 

The query results thus can be easily combined, e.g. in order to prepare a presentation about Napoleon at Waterloo with historical dates from the 
database \p{regents} and text information from the text collection 
\p{politicalEvents}.


\subsection{Personal Reference Libraries}

Digital libraries provide multi-media material for groups 
of information consumers. To secure the success of a complex task 
a working environment tailored to the individual requirements 
of the consumer and to the specific task is necessary. 
The development of such personalized, cooperative working environments 
called \e{personal reference libraries} is currently being examined 
in our group. Personal digital reference libraries
can be stored persistently and exchanged with other 
persons who work on the same or a similar topic.

An example of the construction of a personal reference library is 
the preparation of a publication and/or demonstration
on equestrian portraits of regents throughout the centuries. 

The ontology PI-Index includes the terms \e{Reiterbild}, i.e. equestrian 
portrait, and \e{Herrscher}, i.e. regent. The set of pictures and other 
material classified into both categories can thus be easily accessed
using the services of the digital library. 

In the next step a personal reference library can be created for 
the special task by selecting representative pictures and related 
text material from the different centuries. The selected pictures can be annotated with comments giving, for example, the reason for the choice, or ideas for the publication. Further information such as the date 
of inclusion, the creator of the artifact, and the source of 
the information can be  added automatically from the tracing environment.


Since personal reference libraries are also artifacts (compare figure
\ref{Fig:InformationUniverse}) the different supported binding mechanisms can be exploited to realize the separation between the public scope of the digital 
library and the private tailored scope of the personal reference 
library. 

\begin{itemize}
\item
Remote bindings to relevant paintings 
in other art collections and local bindings to
paintings organized in the \e{PI-Index} can be established and stored in 
local object stores.
\item
Information on artists, available on CD-ROM, may be 
included in the personal library by external references 
in order to gain a better understanding of individual paintings. 
\item
Stored parameterized queries can be used to establish dynamic bindings 
to contemporary paintings of horses and other animals,
evaluating the query on demand for different parameters specifying 
the time frame of interest. 
\item 
Text information about the illustrated event, the 
 regent or equestrian portraits in general
can be included by remote references to entire publications 
complemented by copies of text passages considered important 
for the publication in work. 
\item 
Autonomous bindings (agent technology) can be exploited to search 
further art collections for representative equestrian portraits 
of regents.  The respective agent may be resent periodically in order to retrieve the most actual publications and newly created tokens and 
artifacts. 
\end{itemize}

Personal reference libraries are created stepwise, scanning the 
available material in several sessions, including new more 
adequate tokens and artifacts, possibly rejecting previous choices.

This requires a binding environment that can be updated 
dynamically (inserting and deleting bindings). Dynamic 
environments as proposed in \cite{Dea89} are considered a 
good starting point for the realization of these dynamic 
artifacts. The combination of the various binding mechanisms
with the concept of a dynamic environment is a topic of 
current research. 


 

