appearing in the query).This Web page is updated as the Presentation Manager receives (from the
Answer Issuer) the summary of the results obtained from the databases, showing for each digital
library the number of results that match the query. Once this answer is obtained, users can access
each of the digital libraries to display the documents matching their query, using the digital
library's own interface.
Note the difference between the queries and the answers: while queries are performed in an
integrated way, answers are always displayed using the digital libraries' own interface. As we pre-
viously noted, the administrators of the digital libraries might not be willing to offer their data-
base information through an answer interface different from their own. Furthermore, there will
be cases when the direct link to their answer interface showing the results of the query will not
be available, and the user will have to repeat the query using the interface of the digital library to
be able to display the results. In this case, our system is useful only to locate appropriate sources
of information about the topic of interest.
Actually, since the answer interface of each one of the digital libraries is specifically designed
for its data, those answer interfaces will always be more intuitive and user friendly than any other
interface we can build to display the results from the databases in an integrated way.
A rc h i t e c t u re f o r t h e Fe d e ra t i o n o f M u l t i l i n g u a l
D i g i t a l L i b ra r i e s
We have extended the architecture described above to allow the federation of multilingual dig-
ital libraries.The "multilingual architecture," fully described elsewhere, keeps all the features of
the "original" one.16 It is easy to implement; it is easy to add or remove sources (databases or
XML sources) to the federation; and it allows the development of a useful and intuitive user inter-
C o n c l u s i o n s
We have described in this paper a system to federate a set of digital libraries, initially designed
to federate three digital libraries containing rare Spanish documents from the sixteenth through
eighteenth centuries, but adequate to federate any set of related document databases.The main
idea of the system, the use of XML trees, offers a number of advantages, the main ones being
those that allow our system to accomplish the six aims presented in the introduction.
See, for example, the Emblem
Literature answer interface, note 2.
See N.R. Brisaboa, J.R. Paramá,
M.R. Penabad, A.S. Places, and F.J.
Problems in a Multilingual Digital
Library Federation," Lecture Notes in
Computer Science 2510 (2002): 503-
510, and N.R. Brisaboa, Á.S. Places,
C. F. Pérez-Sanjulián, and F.J.
Rodríguez,"An Architectural Pro-
posal for a Cross-Language System
to Federate Multilingual Digital
Libraries," Digital Libraries Advanced
Methods,Techniques and Technologies,
Electronic Digital Collections. Petroza-
vodsk, Russia 2001. Conference
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