In order for the system to work towards user-based performance goals, a goal-based illuminance
metric was used. This metric is defined as the percentage of time (during the goal time period(s)) and
of total sensor plane area in which the illuminance falls within a user-defined goal illuminance range.
The expert system will attempt to increase the value of this metric through each suggested design
change. A value of 100% indicates that the climate-based illuminance calculated for the given design
is within the goal range for the entire sensor plane area over the entire year (or over the entire set of
goal periods of time). This metric is a numerical version of the graphical metric presented in [10] and
uses the same logic for climate and temporal simplifications. The LSV engine is used to efficiently
calculate this metric within the expert system process.