The Stanford Digital Library Testbed
The Stanford Digital Library testbed is our platform for
experimentation with interoperation among online services. Our basic
approach is to use distributed objects to allow
integrated access to heterogenous services across networks. We call
this system the InfoBus. The distributed approach allows the
interaction of processes on different machines, with different
architectures, implemented in different languages. We use
CORBA to provide communication between remote
processes. In particular, we use Xerox PARC's ILU, a
free implementation of a CORBA superset, MICO, a free
CORBA implementation under the Gnu license, and
Visigenic, a commercial provider.
We use Java, C++, and the interpreted, object-oriented language Python
for our development work. Our computing platforms include Sun,
PC-based architectures, and 3COM Palm Pilots.
For more information on the underlying technologies, see:
- Xerox PARC's ILU Home Page. Link was ftp://ftp.parc.xerox.com/pub/ilu/ilu.html.
What Protocol does the Testbed Use?
We have developed the
Simple Digital Library Interoperation Protocol
(SDLIP) (pronounced S-D-Lip) for information access and
retrieval. It supports both synchronous and asynchronous operation,
providing robustness in the face of network or server outages.
Moreover, it also gives the programmer a high degree of control over
where and when information objects are materialized, affecting
tradeoffs of space and cost vs. time. Protocol bindings are defined
for both CORBA and HTTP. SDLIP is carefully designed so that it can be
implemented even on very small footprint PDAs, but that it can scale
up to serve interactions with complex information sources.
Mobile Access to Digital Libraries
One portion of our testbed is devoted to making digital library
resources available everywhere a user travels. We are developing
proxies that prepare information for transmission over low bandwidths
to portable digital assistants (PDAs) with very small screen
real-estate. A part of this effort includes support for secure
transactions between PDAs and online services.
We have developed a
software library that supports our work on the 3COM Palm Pilot. It
includes facilities for memory management, event handling, TCP/IP
communication, and XML parsing. We are also working on DietORB, a
scaled-down CORBA ORB for the Pilot.
Publicly Available Software Services
- InterBib. A
bibliography tool for converting bibliographies among various
formats. The tool also processes RTF and Framemaker files, including
bibliographies when given a BibTeX bibliography source. This extends
LaTeX's BibTeX capability to MS-Word and Framemaker documents.
Various Operating Instructions