The focus throughout is the development of understanding, rather than as some sort of by-product. Central to this is the notion of documentation. This can be split into four practices: observing, recording, interpreting and sharing. What is important about documentation is that it, βmust serve to advance learning, not merely capture it. As such, documentation includes not only what is collected but also the discussions and reflections on those artifacts.β (Page 38)
Source: An Introduction to Making Thinking Visible – Read Write Respond by Aaron Davis
Another book that I have dived in and out of on the topic has been The Hundred Languages of Children: The Reggio Emilia Experience in Transformation, a book that brings together a number of voices on various topics, including Part III, which is on documentation.