Rocket Scientist Marshall T. Rose is Chief of Protocol at Invisible Worlds, Inc. where he is responsible both for the Blocks architecture and the server-side implementation. Rose lives with internetworking technologies, as a theorist, implementor, and agent provocateur. He formerly held the position of IETF Area Director for Network Management, one of a dozen individuals who oversee the Internet's standardization process. His current book is Internet Messaging (Prentice Hall).

       This edition of Rocket Science features space.cgi, the Invisible Worlds interface to the SpaceServer. A general introduction to SpaceServers and other components of the Blocks Architecture are in this issue in the article entitled The Importance of Being EDGAR. We recommend reading that piece before proceeding into the material in this section. Caveat: this section contains advanced material, aimed at developers.

       The EDGARspace portal and the Danny Goodman SpaceKit are both examples of applications that use space.cgi, the web proxy interface to the SpaceServer. This Rocket Science feature documents how you can write your own applications that access the SpaceServer.

       The core concept to understand is the retrieve, evaluate, publish paradigm. All calls to space.cgi exercise this paradigm: data are retrieved from the SpaceServer. The metadata are fed into an evaluate script (or a series of scripts) to look for relationships among the data, then the results of the evaluate stage are fed into the publish stage for formatting.

       To understand how to write to this paradigm, you will need to understand several basic concepts:

space.cgi Basic Concepts
Tutorial		The space.cgi tutorial explains the basic format of a call to space.cgi and the different styles of retrieval.
Scripts		The scripts tutorial shows you some basic evaluate and publish scripts that we have developed, which you can use as - is or as the basis for writing your own scripts.
Union Operator		The union operator is an advanced form of retrieval, where you specify the nature of your query using XML.
XML DTDs		XML DTDs define the structure of data stored in the SpaceServer. By looking at these DTDs, you can see what types of queries are possible.
Examples		Examples give you a few canned queries. For those of you that hate documentation, this is a good place to start!