Design and Software Development
After a preliminary study (1992/1993) and the installation of a local
prototype (1993), the project has now started its development phase.
The architecture is based on the client-server philosophy which,
optimizes access to distributed computing resources and
offers modularity and flexibility, thus making much easier
further hardware and software evolutions of the system.
ALADIN is composed of 5 main pieces of software :
a graphical user interface,
the CDS multimedia server,
the Image database server,
the Catalogue server
and the SIMBAD server.
Communications between the user interface and the CDS server, and
between servers and databases, are designed according to the
The access to the system from the outside world
is managed by the ``CDS multimedia server'' which is
connected to each dedicated server through the CDS local network.
- The SIMBAD server:
The SIMBAD software was not originally (1988) written following this
client/server approach: a server mode has been recently added to
the ``user interface class" (Bonnarel et al. 1994).
In order to make easier the development of new user interfaces to the
database, a set of client routines
has been developed on top of the communication layer of SIMBAD.
allow to retrieve objects on the basis of identifiers or coordinates,
and to extract the corresponding data
(defined by simple ``astrotypes") and the full bibliographical
- The Catalogue server:
The CDS maintains since 1972 an archive of astronomical
catalogs in machine-readable form, currently yielding a collection
of over 650 catalogs.
The requests issued by ALADIN for extraction of data from the
astronomical catalogs are essentially based on the following two
choice of the catalogs to be scanned, according to a predefined purpose
(e.g. catalogs for photometric calibration, with IR data, etc.),
and region of the sky to be examined.
- The Image Database
is currently under development. Its main function is to
retrieve sets of images according to astronomical
criteria: survey, color, region of the sky, etc.
The selection of the
images is made using Image Qualifiers stored in a relational database.
In order to give a great modularity to each step of the request,
an object oriented design has been retained for the software.
Image Set, Image Qualifier, Image Archive and Image are the basic
classes of the software.
- The CDS multimedia server
is the common gateway to all the
databases and archives of the CDS. An object
oriented design has also been retained for this software.
- The User Interface
is an X-Window/Motif distributed client, providing
Image Display functionalities and various menus for querying the
CDS databases and archives and displaying the data and images.
Astronomical packages, such as astrometric and photometric calibration
tools, source extraction, classification, will also be provided.