Development and implementation of an information server for web-based education in astronomy

Abstract

This paper focuses on the development of a high-performance information server for web-based education. An innovative model of software architecture is provided to effectively utilize the computational power of a parallel server platform for efficient, on-demand astronomical image browsing through the Internet. Our previous research revealed the demand for astronomical image browsing raised by various communities engaged in educational and research activities. Additionally, we have characterized network performance under different levels of activity and identified techniques for efficient image transmission over the Internet. Based on our findings, we have developed a parallel server which will handle an arbitrary (typically large) number of simultaneous requests for astronomical image files from distributed clients. The server is capable of disseminating data at different transmission rates to accommodate the various network bandwidth restrictions, real-time display requirements, and/or image resolution requirements of different communities. In our design, a tuple space programming paradigm is used to enable parallel processing of the image browsing requests. This architectural model supports automatic load balancing to fully utilize the computational power provided by the parallel server. Additionally, a hashing algorithm is used for fast look-up of astronomical image files in the database. Since different image resolutions and transmission rates may be required, multiple worker processes (known as threads) are employed to perform progressive, on-demand image decompression and transmission using a wavelet-based transformation algorithm. This approach facilitates efficient use of system processing and communication resources while providing the flexibility to serve a diverse clientele. The various service parameters can be explicitly defined by the client or implicitly analyzed by a controller thread on the server side, thus providing the "best effort delivery" given realistic constraints. © Springer Science+Business Media B.V. 2008.