Databases and Systems

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which is functionally equivalent to the graphic Acedb code but gets its data
transparently from a remote server.
Xclient must be installed on the client machine. When the xclient is running, data
is imported on the fly from the distant server and used to construct a local database.
The resulting system is fast, even on a slow network, because most actions operate on
locally cached data. Xclient can be used in two ways. Inside the lab, it allows
multiple clients to get simultaneous write access on the server, a feature that was
lacking in xace. Over the network, it allows users to access the latest data without the
need to download a complete data set. Xclient may be downloaded from our Web
site. By default, it is configured to access our C.elegans server. Instructions to
redirect the client or to create a new server are included.
Web interface
The standard graphic acedb, xace, uses the X11 protocol. It does work over the
network but only by starting a big process on the server side, which is costly and
requires special privileges. Xclient, described above, needs to be installed before it
can be used and only runs on Unix machines. In this section, we explain how Acedb
databases can be viewed over the Web using conventional Web browsers, without
any special effort from the end user.
The first implementation of Acedb over the Web was written as early as 1992 by
Guy Decoux. Called the Moulon server, it was surprisingly complete but very slow,
because a new Acedb process was started to process each request.
When the aceserver became available, Doug Bigwood's group at the National
Agriculture Library–developed Webace. We wrote together a special module to
export Acedb objects in a form that could be compiled into Perl objects by the Perl
interpreter. These objects were then enriched outside of Acedb by other-Per1 layers
that add hot links. For example, GenBank accession numbers are automatically
converted into links to NCBI Entrez pages. Webace also allows several Acedb
databases to be browsed simultaneously. The downside of Webace is that installation
is somewhat complex; however it is very powerful and the NAL Webace server is
actively used to access data concerning a large number of cereals and other
interesting plants. Webace is now maintained by Tim Hubbard
http://webace.sanger.ac.uk.
Two years ago, we started with great enthusiasm to work on a Java interface to
Acedb. We designed a system called Jade [7] which may be used to browse different
types of servers, including Acedb databases, relational databases, or even simple flat
files. The low-level interfaces that allow Acedb objects to be converted into native
Java objects are complete and quite useable, but the development of a graphical user
interface to replace the xace displays has lagged behind. This is partly because of the
immaturity of the Java abstract windowing toolkit (AWT), and partly because we