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Ganghua, L. 2001, in ASP Conf. Ser., Vol. 238, Astronomical Data Analysis Software and Systems X, eds. F. R. Harnden, Jr., F. A. Primini, & H. E. Payne (San Francisco: ASP), 392
A System for Web-based Access to the HSOS Database
Ganghua Lin
National Astronomical Observatories,
Chinese Academy of Sciences, Beijing,China
Abstract:
Huairou Solar Observing Station's (HSOS) magnetogram and dopplergram
are world-class instruments. Access to their data has opened to the world.
Web-based access to the data will provide a powerful, convenient
tool for data searching and solar physics. It is necessary that our data
be provided to users via the Web when it is opened to the world. In
this presentation, the author describes general design and programming
construction of the system. The system will be generated by PHP and MySQL.
The author also introduces basic feature of PHP and MySQL.
Huairou Solar Observing Station's (HSOS) magnetograph can simultaneously
measure the solar 2-D magnetic field and velocity field with
different spectral lines. The photospheric vector magnetograms and
dopplergrams, chromospheric longitudinal magnetograms and dopplergrams,
and corresponding filtergrams can be obtained by this system. So far, 13 years
of observations have been obtained.
Because of the international character of astronomy, we are planning to
develop software that is independent of the archive architecture and which
provides users with Web access capabilities.
Given the large amount of data, and that
the data is not only plain text but also
image file, visual file, we select a relational
database--MySQL--to build the database management
system, and use PHP to build the
database engine and user query interface.
The final system is expected to allow users to get good response
time and easy browsing of the HSOS on-line database by
the means of a Web-based user interface, display results graphically,
and save them locally for further analysis.
In Figure 1, we give an overview of the architecture of
the system:
Figure 1:
Architecture of the HSOS database on-line system.
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- content of the database;
- the database structure being developed;
- the extensions we are developing to the database engine to support
HSOS data and queries;
- access methods;
- access interfaces currently under development.
In the following sections we briefly describe the items shown as
rectangles in Figure 1.
At present, only the data which are currently being used or built in the HSOS
database project are foreseen to be included in the database. They
are: photospheric longitudinal magnetic field data, photospheric filtergram
image data and photospheric transverse magnetic field. Other data, for
example, chromospheric longitudinal magnetic field, filtergram image,
longitudinal velocity field data, etc., may be added in the future depending on
users' requirements. Users can learn more about HSOS data through reading
the the on-line README file.
All data in the collection are described in a metadata structure we call
the metadata table. All applications will access the database
through the table, so that they will work independently of any data-specific
structure. Using a table will also simplify the addition of new data to
the collection. Metadata access has been developed in the PHP language.
All the data in the collection are managed by means of the
MySQL
relational DBMS. The database engine can be extended by
means of software modules that plug in to MySQL Dynamic Server and extend
its capabilities in order to store, retrieve, and manipulate new data
types, besides the primitive ones provided with the server. These modules
are transaction manager, retrieve server, database manager, save server, and
print server.
We are following the recent efforts directed at giving users
direct access to HSOS database through the HSOS Web site. We will give
users integrated access to world-wide distributed astronomical data
collections. Our efforts will be directed to providing open access to the
system by means of standard interfaces. In our view, this is the
most effective way to maximize our system's utilization.
We are currently prototyping simple WWW-based clients able to submit
queries to the on-line system. These clients are implemented in
PHP.
In this way, users are not required to
install special
client software and more interactivity is possible at the user
workstation level. After this prototyping phase, we plan to design and build
more sophisticated, intuitive interfaces to allow users to submit complete
queries to the database, possibly in a graphical way.
PHP has the following useful features:
- PHP is a server-side, cross-platform, HTML embedded scripting language;
- Much of its syntax is borrowed from C, Java, and Perl, with a couple of
unique PHP-specific features thrown in. It has powerful
database access functions. It is easy to learn;
- It has nearly all the features needed for building a Web site:
designing objects, database access, network protocols, and security.
Its quick response time, multi-threaded nature, and transparency to the end user
make it ideal for developing dynamic Web sites and
applications.
The critical factors for a database management system are:
- Performance. A lot of clients can connect to the database server at the
same time. Clients can use many databases simultaneously, and submit
many queries;
- It should support SQL and ODBC;
- Connectivity and security. Its database should can be accessible and
shared by anyone on the Internet.
MySQL offers a rich and very useful set of functions. The
performance, connectivity, speed and security make MySQL highly suited for
accessing databases on the Internet. MySQL is a client/server system that
consists of a multi-threaded SQL server that supports different backends,
several different client programs and libraries, administrative tools, and a
programming interface.
PHP and MySQL work with each other very well. Both PHP and MySQL are open
source software. In combination with our Linux operating system, they
form a ideal network database environment.
© Copyright 2001 Astronomical Society of the Pacific, 390 Ashton Avenue, San Francisco, California 94112, USA
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