SDSS currently uses the VERSANT1.50exTM object-oriented distributed database [6] to maintain various catalogs of data used throughout the collaboration. Convenient access to these is provided through a set of hierarchical HTML forms: selecting the database, selecting a class within the database, providing selection criteria to locate class instances, etcetera. The database requires accesses to it to be made in the scope of a session from the same task. As the server is stateless (it does not maintain state information between form submissions), initiating a session for each query is too time consuming. Rather, the initial form spawns a persistent task which is used to maintain the context of the database session.
Databases are not restricted to those generated by the Survey.
As an example, the Guide Star Catalog (GSC) [5] is available.
Providing the coordinates of a star (
),
an epoch, a field size, and a magnitude limit (Figure 1a),
one can get an inline finding chart of that portion of the sky
(Figure 1b).
Figure 1: a) GSC Query near Betelgeuse and b) Resulting Chart