A Literate Programming (LP) "Hello World" Example

Allegra is being written using literate programming development methods. For those unfamiliar with this technique, or who have not used Norm Walsh's DocBook/XML-based LitProg LP system with Ada, we have created a small "Hello, world" example to illustrate the process. There are three files associated with this example:

• helloworld.xweb - The initial XML source file from which the other two files were created. This is the part that I edit to update the program or the documentation. I created it using XEmacs's PSGML mode and this DTD, which comes with the LitProg package. It's really just a DocBook XML source document, with a couple of tags that Walsh's XSLT stylsheets recognize. I use the GNOME project's xsltproc stylesheet processor to do the tangling and weaving.
• helloworld.adb - The actual Ada source program created by "tangling" the XML source. It's totally trivial, and I never edit it directly.
• helloworld.html - The program document, including the "user guide" and the design/maintenance documentation, created by "weaving" the XML source. As with the source, I never edit this file directly. It includes more links to the related software and concepts.