85th AMS Annual Meeting

Tuesday, 11 January 2005
Using the Climate Data Analysis Tools (CDAT) to distribute Earth Science Data and Diagnosis via: Live Access Server, Zope or Mod_python
Charles Doutriaux, PCMDI, Livermore, CA; and D. N. Williams, A. Stephens, and B. Tang
With the recent progress in computer technologies, the volume of data produced by climate models simulation has grown considerably.

As a result, in recent years, there has been a growing interest in serving data and diagnosis over the internet; and multiple, new, technologies emerged to do so. In this study we looked at three possible ways to distribute such information: The Live Access Server, Zope and Mod_python.

Since 1994 the Live Access Server (LAS) has been providing visualization and subsetting of multi-dimensional scientific data for Web users. Chief among the initial design goals of LAS was to break through the data access barriers of file size, location, and format by providing three key areas of functionality: visualization, subsetting, and reformatting. On-the-fly visualization makes it possible to explore the data set entirely within a Web browser environment. Should further analysis at the desktop be desirable subsetting allows the scientist to download small units of data that move efficiently on the Internet. Reformatting makes it simple to ingest the data into the scientistís choice of desktop environments.

Zope is an open source web application server primarily written in the Python programming language. It features a transactional object database which can store not only content and custom data, but also dynamic HTML templates, scripts, a search engine, and relational database (RDBMS) connections and code. It features a strong through-the-web development model, allowing you to update your web site from anywhere in the world. To allow for this, Zope also features a tightly integrated security model. Built around the concept of "safe delegation of control", Zope's security architecture also allows you to turn control over parts of a web site to other organizations or individuals. The transactional model applies not only to Zope's object database, but to many relational database connectors as well, allowing for strong data integrity. This transaction model happens automatically, ensuring that all data is successfully stored in connected data sources by the time a response is returned to a web browser or other client.

Mod_python is an Apache module that embeds the Python interpreter within the server. With mod_python you can write web-based applications in Python that will run many times faster than traditional CGI and will have access to advanced features such as ability to retain database connections and other data between hits and access to Apache internals All three of these systems can be and have been tied to the Climate Data Analysis Tools (CDAT) developped at PCMDI. We looked at the different strengths and weaknesses of each system, such as installation process, usability, speed, etc...

As a result we tried to summarize which solution is most adapted to various data/diagnosis distribution problems.

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