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Heikkila, C. W., McGlynn, T. A., & White, N. E. 1999, in ASP Conf. Ser., Vol. 172, Astronomical Data Analysis Software and Systems VIII, eds. D. M. Mehringer, R. L. Plante, & D. A. Roberts (San Francisco: ASP), 221
Astrobrowse: a Web Agent for Querying Astronomical Databases
Christina W. Heikkila1, Thomas A. McGlynn2, Nicholas E. White
NASA/Goddard Space Flight Center, Greenbelt, MD 20771
Abstract:
Astrobrowse is a user agent which significantly streamlines the process of gathering
astronomical data on the web. With it, a user can query thousands of resources
without having to search through old bookmark lists, deal with out-of-date URLs,
or spend time figuring out how to use each resource's unique input form. Given
a user's selection of web-based astronomical databases and an object name or
coordinates, Astrobrowse will explode queries to all selected databases and
collect the results. Since the introduction of the prototype at ADASS VII
(McGlynn & White 1998), many changes have been made to the service, from
adding JavaScript form validation, to the adoption of GLU
(Fernique, Ochsenbein & Wenger 1998)
as the mechanism for keeping the resource URLs current.
This software is freely available to anyone wishing to become an Astrobrowse
node.
With the ability to query astronomical databases and catalogs online becoming
more and more the norm, it has become daunting to try to keep track of all
these queryable services. A bookmark list with all these forms and data
centers can become unmanageable. It is also likely to become out of date,
since web addresses are frequently changing. In addition, most of
these query forms have different formats, requiring the user to learn how to
use a different form at each new query site. Often the user must enter
positional data in particular formats or epochs: one site may ask for decimal right ascension and declination,
while another requires sexagesimal (hh mm ss) coordinates.
To address these problems, the Astrobrowse effort was developed with close
cooperation by many institutions. Some of the involved groups are:
HEASARC, ADF, STScI, CDS, SAO, IPAC, LEDAS, and CADC. HEASARC, STScI, and CDS
each have their own versions of the Astrobrowse software, and SAO and LEDAS are
running the HEASARC version.
We have already compiled a large list of position-searchable databases
on the web. When a new one is suggested,
a web form is filled out by the Astrobrowse administrator or by the person
suggesting the new site, and the Astrobrowse software converts this to the
correct format.
URLs are kept current through the CDS's GLU server software. This software
propagates changes in the database descriptions to all Astrobrowse GLU network
members, enabling Astrobrowse to use the latest available URLs when querying databases.
Astrobrowse takes care of converting the user's object name or position into the format
and epoch required by each remote query service.
Considering the amount of time expended to find, load, and fill out
a large number of suitable query forms, the time savings for the user
become significant,
since with Astrobrowse the user only fills out one form to retrieve the same
amount of information.
Using the HEASARC version of Astrobrowse,
the user can choose to query from the menus of resources provided,
or to create a custom resource list using a search tool. The
search tool allows the user to search for only X-ray resources, for example, or
only resources serving images, or ones holding data from a particular satelliteions
Once a list of resources is displayed, the user chooses which ones to search
via checkboxes, and enters either an object name or
coordinates. Astrobrowse then formulates a query to each data service:
looking up the object name (if given) via SIMBAD or NED, converting the object
coordinates to the format specified by the remote service, and providing
additional form input needed by the remote service.
Each query is sent by
Astrobrowse in parallel, and as the results are received by the remote services,
each is saved on the server machine. The user is shown a framed results
page, with an index to the results shown in the left frame, and each individual
result shown in the right frame as the user clicks through the index.
The user can switch back and forth easily between results, or pop up new browser windows for side-by-side comparisons.
The resource description database used by Astrobrowse is maintained by the CDS's GLU network software.
This software allows each network member to change the entries owned
by them as needed, and GLU distributes the change to all other members.
The system is not hierarchical, so if one member institution experiences
network problems, no one else is affected. Currently there are eight members in
the Astrobrowse GLU network. In addition to the URL and form data needed for the query, the GLU resource description entries
carry metadata specifying additional URLs (such as help documents), email
addresses of maintainers, server location, etc. The software is freely
available from CDS.
HEASARC Astrobrowse sets a cookie which stores the names of the catalogs the user queried
last, so if the researcher wants to do a search for data on more than one
object, he or she doesn't have to remember which catalogs were selected for
the previous source. The cookie expires after one month.
JavaScript functions have been added to the keyword search form and the catalog
selection form in HEASARC Astrobrowse. These functions check to make sure the user has specified
necessary input in the correct format before submitting a request to the
server. Since the form validation is done on the client side, this saves the
user time - the user doesn't have to wait for the server to receive the
information, decide that there's a problem, and return an error message. This
arrangement also reduces the load on the server machine, since only valid
requests should be sent to the server. These JavaScript additions have been
designed to be cross-browser compatible, and the software will still work
with server-side form validation in case users run their browsers with
JavaScript disabled.
We are investigating allowing non-positional queries in Astrobrowse; already
some databases are queryable by object name.
More resources are continually
being added to those queryable through Astrobrowse, there are currently more
than fourteen hundred.
We have made the HEASARC Astrobrowse software available to download from its
web site. We encourage other institutions to install the software
and provide the Astrobrowse service.
We have recently been granted funding for a design
study on ISAIA (Interoperable Systems for Archival Information Access), which
will build on the Astrobrowse concept. ISAIA will have the ability to search
on many different metadata parameters, not just position. It will integrate
the results received from remote providers into unified tables of data - making
interpretation of the data much faster and easier.
References
McGlynn, T. & White, N. 1998, in ASP Conf. Ser., Vol. 145, Astronomical Data Analysis
Software and Systems VII, ed. R. Albrecht, R. N. Hook, &
H. A. Bushouse
(San Francisco: ASP), 481
Fernique, P., Ochsenbein, F., & Wenger, M. 1998, in ASP Conf. Ser., Vol. 145, Astronomical Data Analysis
Software and Systems VII, ed. R. Albrecht, R. N. Hook, &
H. A. Bushouse
(San Francisco: ASP), 466
Footnotes
- ... Heikkila1
- Raytheon ITSS, Email: cwh@lheamail.gsfc.nasa.gov
- ... McGlynn2
- Universities Space Research Association, Email: tam@silk.gsfc.nasa.gov
© Copyright 1999 Astronomical Society of the Pacific, 390 Ashton Avenue, San Francisco, California 94112, USA
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