// The segment is of the type (query) 
SegType(seg,type)
// The segment is part of the line (query)
PartOf(seg, line)
   
// The angle between two segments is below some threshold, 
// and so is the perpendicular distance between them (evidence)
Aligned(seg,seg)

// The length of the segment (evidence)
Length(seg)

// The depth of the segment, i.e., the signed perpendicular distance of the
// segment's midpoint to the nearest line (evidence)
Depth(seg)

// Segment can only be of one type
SegType(s, Wall) v SegType(s, Door) v SegType(s, Other).
SegType(s, t) ^ t != t' => !SegType(s, t').

SegType(s, +t) 

// Aligned wall segments tend to be part of the same wall line
SegType(s,Wall) ^ SegType(s',Wall) ^ Aligned(s,s') ^ PartOf(s,l) => PartOf(s',l)

// Typical lengths and depths of door and wall segments
SegType(s, Door) * -(Length(s) - 0.1)^2
SegType(s, Door) * (Depth(s) = 0.02)
SegType(s, Wall) * (Length(s) = 0.341)
SegType(s, Wall) * (Depth(s) = 0.001)