I read a paper once (at the University of New Brunswick (Canada)) library in which the grammar for a language was used to construct a data compressor for syntaxly correct programs. The output was a compressed form of a parse/syntax tree with comments and white space included. Once decompressed, the tree could be used to reconstruct the source. I don't know if a compressed syntax tree would be very useful for programming tasks but it could be used to compress Smalltalk's source file and changes file. This assumes the time saved by filing in smaller chucks of programs segments would greater than the cost of decompression. I am designing and planning to implement a parser generator tool (yes, another parser generator tool, something the world really needs ;-) ). If/when this project is complete perhaps I'll give this compressed AST idea a try. Convincing the Squeak/Pharo world that it should be used is another matter entirely. Ralph Boland