Oh Oh--deviating from system set-up talk again... note to self--don't make habit of this...
In science education we often talk about a 'spiral curriculum' where the timeline of our activities instead of being a simple straight line is instead a spiral going up... (think Helix). This means different things to different educators. Look at this drawing (thanks to http://www.cut-the-knot.org/Mset99/spiral.gif):
This shows that as time goes on (in this drawing each loop is a full year), students repeat working on the same skill--addition--but presumable in more complex contexts. Another example of a spiral curriculum shows another aspect, how different 'sides' of the helix represent different concept or skills, as well as maybe how one might organize over the length of a unit, maybe 3-4 weeks or so:
(this drawing is thanks to: http://uwacadweb.uwyo.edu/CLAAS/Old%20stuff/bigspiral.jpg). In this example, Literacy 1 might be 'Graphing', Literacy 2 might be the concept of Heat Transfer and Literacy 3 might be the skill of 'searching on the internet'.
I've tried to plan a unit like this in the past using a spiral drawing but couldn't get it to work--I didn't really try that hard either. I think, however, that if there were some software that provided control over the spiraling time-line, mixing spirals, threads shown, snap-in placement, changing radius of spiral, adjusting colors of the vertical 'literacy's' well, one could have a powerful visualization tool for unit/curriculum planning. This would be a nice way to share our units and help practitioners (ie teachers) implement the curriculum. For those who aren't teachers, teachers have to be able to adjust from moment to moment what we are doing in the class to take advantage of the possibilities of the moment and meet the needs as they arise. All of this has to be done, of course, with the larger curricular goals in mind. Yes, so this tool could help one have those larger goals in mind.
Update: thought I would add this info here, as well:
By far the most interesting and useful spiraling model is called, "Progressive Inquiry". It is perhaps the most difficult spiral curriculum approach to implement as it is a distinctly different from traditional approaches. Interestingly it is organized and thought of from the perspective of the classroom as a community. This is the instructional model that we'll be using here at GCoS. Check this site for info. Here's a drawing they produced to help explain the approach: