Per agent cumulative isovist refers to the mean fraction of building area that could have been viewed by an agent during its visit, that is, the cumulative isovist area for the agent during its 1800-step lifespan, expressed as a fraction of total floor area.
Per agent cummulative isovist
Turner, A. & Penn, A. (2002), Encoding natural movement as an agent-based system: an investigation into human pedestrian behaviour in the built environment. Environment and Planning B: Planning and Design 2002, pp. 473-490.