Proximal formative assessment

I am very taken with this chapter by Erickson on formative assessment.  The focus is on "proximal" formative assessment, which is the moment-to-moment stuff - most of what concerns us in video analysis.  Thanks, Kara:

Erickson, F. (2007), chapter 8 Some Thoughts on “Proximal” Formative Assessment of Student Learning. Yearbook of the National Society for the Study of Education, 106: 186–216.  Link