OPeNDAP User Guide -- 5 The OPeNDAP Server

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5 The OPeNDAP Server

See the OPeNDAP Server installation guide for most of this information.

There are two separate pieces to the task of installing an OPeNDAP data server: installing and configuring the server itself, and telling the universe of possible users about it.¹³ Only the first will be considered in this chapter. OPeNDAP provides avenues for doing the second, including a Catalog Service indexing OPeNDAP datasets, and cooperation with the Global Change Master Directory, but these are still under construction.

An OPeNDAP server is nothing more than a World Wide Web server (httpd) equipped with Common Gateway Interface (CGI) programs that enable it to respond to requests for data from OPeNDAP client programs. Web servers and CGI programs are standard parts of the Web, and the details of their operation and installation are beyond the scope of this guide. For further information about these, consult one of the many World Wide Web references now available. For the purposes of understanding the OPeNDAP architecture, a user need only understand the following:

A Web server is a process that runs on a computer (the host machine) connected to the Internet. When it receives a URL from some Web client, such as a user somewhere operating Netscape or Mosaic, it packages and returns the data specified by the URL to that client. The data can be text, as in a web page, but it may also be images, sounds, a program to be executed on the client machine, or some other data.
A properly specified URL can cause a Web server to invoke a CGI program on its host machine, accepting the input that would have gone to the httpd, and returning the output of that program to the client who sent the URL in the first place. The CGI is executed on the server. The OPeNDAP server relies on this facility.

Tom Sgouros, August 25, 2004