Describe the two key principles of the Boxer system.
The two key principles of the Boxer system are the spatial metaphor and naive realism.
The first basic metaphor of hypertext -- Vannevar Bush's "associative trails" -- is a spatial metaphor, which recognizes and uses the ability of people to understand a concept through visualizing it in the physical world. By providing people with a vision of following a trail (the idea) through a forest (the data), Bush helped them to see the possibilities of what would later be called hypertext.
Abelson and diSessa use this same kind of navigational metaphor in their Boxer system, encouraging people to see the non-linear relationships of hypertext as spatial relationships. The Boxer system represents computational objects as boxes; containers that hold text, graphics, or other boxes (boxes within boxes denote a hierarchial relationship). Each box is an entity unto itself, and users can build programs by putting the boxes together (or taking them apart) in various configurations.
Vannevar Bush's influence on the Boxer system continues beyond the idea of associative trails. Boxer also incorporates Bush's desire to mechanize repetitive work, by relying on naive realism to make Boxer more comprehensible to the user. The basic principle of the Boxer screen display is "what you see is what you have" -- in other words, the Boxer system hides the programming code from the user, showing only the programming results. By working at this level of abstraction, the user can focus on the creative work he wants to do without worrying about the cumbersome and repetitive details underneath it.
Why is Boxer an important system in the hypertext literature?
The Boxer system is important in the hypertext literature because it lays out the principles of user-friendly programming and provides a prototype for how such a programming system might work in practice. Like Smalltalk before it, Boxer is an effort to democratize computer programming so that even non-professionals can use powerful computer-based tools to do creative work.
Boxer is also notable for its use of object-oriented programming techniques as a means of cutting down on the time and frustration involved with programming. The idea of chunks of code being copyable and re-usable modules (or "boxes") makes programming easier for professionals and amateurs alike.
Boxer as a programming language can be seen in some ways as a forerunner to html, which, like Boxer, is easy to learn, easy to "debug", and focuses on presentation.