Under OPeNDAP, there is no central archive of data. Data under OPeNDAP is organized in a manner similar to the World Wide Web itself. That is, all one need do to make one's data available is to start up a properly configured httpd server on an Internet node that has access to the data to be served. Each data provider is free to join and to leave the system when it is convenient, just as any proprietor of a web page is free to delete it or add to it as whimsy demands.
Of course, as can also be seen on the World Wide Web, there are some
disadvantages to the lack of central authority. If no one knows about
a web site, no one will visit it. Similarly, listing a dataset in a
central data catalog, such as the Global Change Master Directory
(http://gcmd.gsfc.nasa.gov/),
can make data available to other researchers in a way that simply
configuring an OPeNDAP server does not. OPeNDAP provided a facility for
registering a data set with the GCMD catalog, which makes the data set
known to the OPeNDAP data location service.
The remainder of this book will be divided into three major sections: instructions on the building and operating of OPeNDAP clients; a tutorial and reference on running OPeNDAP servers and making data available to OPeNDAP clients; and technical documentation describing the implementation details (and the motivation behind many of the design decisions) of the OPeNDAP software.