Querying / Selecting Lines

[Eric Katherman]

What would some of you recommend for selecting or querying lines that I have
stored in PostgreSQL?  I can come up with some creative "point to point
guessing" solutions for horizontal and vertical lines but the difficulty
comes with angled lines.  The tolerance becomes an issue too because the
users rarely would actually select the exact point between two line points.

E.g.

myline = -----
user selected point = *
line point = O

(100 200) O----------------------*-------------O (200 200)

Are there some functions built into PostGIS/PostgreSQL?

Eric