The best way to think of ART attributes is as normal material settings that are too new to have their own settings in the material editor. Steve has provided a way to apply these ART attributes without the necessity of redesigning the material editor interface, by directly defining variables in the code using the Attributes interface accessible by clicking the Attributes button in the Material editor.
The link below opens the ART documentation (a link to this was provided in an earlier post) which explains the different settings, and also provides downloadable examples for you to examine. I STRONGLY recommend you download these examples and see how the various attributes have been created and what they do. With the documentation, the discussion forum, and the examples, you should have more than enough info to understand the concept, certainly there is no better way to explain it.
http://www.anim8or.com/download/preview/art_raytracer.htmlNote: The ART attributes, like reflectivity, will ONLY be visible in a render, not on your interface.