ZigZag is Ted Nelson's trademark on a data model he has designed for computer interaction, both for users and between programs. The design is centered around an information structure called a zzstructure and its interactive visualizations. Nelson's stated goal is on one hand a platform for the Project Xanadu hypertext and on the other a complete computing system built on new conventions. Instead of the conventional textual formats and tree structures, zzstructure is a multidimensional extension of a spreadsheet whose cells can contain various kinds of data.
is similar in form to a doubly linked list
that is linked doubly along multiple axes (each dimension corresponds to a single back and forward link, and there are an arbitrary number of dimensions). Each node exists on all dimensions, though it may or may not be connected to anything in that dimension.
Ted Nelson designed a data structure in 1965 and later generalized and applied it in ZigZag. The first prototype consisting of two character-graphical views was implemented by Andrew Pam in 1997. From 2000 to 2003, a free software
project GZigZag (later Gzz) developed another prototype with more views and other conventions. The underlying zzStructure is a patented technology. After 2003, prototype development has continued in various other projects.