Plantinga proposes that:

In general, open structures are more episodic, meandering, and idiosyncratic than their formal counterparts, although no film can avoid formal structure all together. Formal structures are motivated by the requirements of conventions of composition. Open structure may be motivated in various ways, by the filmmaker’s associations while filming, by an anthropological experiment or a journey, or by pure chance.(1997 pp.145–6)

…

An open structure, as Plantinga (1997) points out, still requires some type of coherent order. Plantinga states that a ‘pure open structure would render the projected world formless, as though observation had occurred without the direction of the filmmakers’ (1997, p.135). The observational documentaries of Frederick Wiseman are used by Plantinga (1997) as examples of works that successfully explore an open structure for cinema and television viewing. Plantinga cites the example of Wiseman’s Law and Order (1969) as a demonstration of some of the characteristics of an open structure. In Law and Order Wiseman documents and edits together the activities of an urban police unit, following his own perceptions of the activities that take place. Plantinga (1997) proposes that Wiseman’s portrayal contradicts a formal approach taken towards this topic, which would potentially provide context and details of activities that occur in a systematic and clearly defined order. Open structures typically do not rely on narrative causality or establishing a logical ordering of events. The beginning and ending of the work are not necessarily used to provide context for the viewer as they are in formal structures. Plantinga (1997) argues that each sequence of shots in Law and Order is equally important, in contrast to formal structures that use techniques such as voice–over to make some parts more important than others. These characteristics of an open structure draw attention to filmmakers like Wiseman using editing to experiment with the form of documentary and how a topic is communicated to the audience within a linear structure.

Selected excerpts from:

Keen, Seth. “Netvideo Nonvideo Newvideo Designing a Multilinear Nonnarrative Form for Interactive Documentary.” Doctorate. RMIT University Print. p. 6-7