\label{Cascading_Parameters}

LON-CAPA uses a powerful and flexible {}``cascading parameter''
system. A {}``parameter'' is anything that can be set for a problem
in a course, such as a due date. LON-CAPA parameters can be set for
the {}``entire course'', for {}``all problems in a particular sequence'',
or for an {}``individual problem''. Fully independently of that,
they can be set for {}``everyone in a course'', for {}``everyone
in a section'', or for {}``a single person''. More specific parameter
settings override more general ones.

Some of the more common parameters include {}``open date'' (when
a problem becomes visible for the student to complete), {}``due date''
(the time the student must have the problem done by), {}``answer
date'' (an optional date where the solution to the problem becomes
visible if they did not complete it earlier), and {}``weight'' (the
point value of the problem). Different problem types can also take
different parameters; for instance, the instructor can override the
{}``tolerance'' for a numerical problem (how close the student must
come for a numerical problem to be considered correct), or control
the style of the problem (for instance, the system has an {}``exam''
mode where it will give the student multiple choices for a numerical
problem, which is useful for printed exams). Problems can also export
arbitrary other parameters, which may give instructors the ability
to control the difficulty level or select a specific varient of the
problem, depending on how the problem was authored.

This parameter system makes most common manipulations of these parameters
very easy. If a specific section missed a lab because of a fire drill,
that section can have its due date extended for the week without affecting
any other section with a single operation. A single student can have
their problems opened earlier if they're going to be gone for some
excused reason. An entire self-paced learning course can have a global
due-date set at the beginning of the course.