xowf-procs.tcl

Support for pool questions in the test-item family

Features:
- select random questions from some folder
(Currently siblings, i.e., folders of the same package instance)

- one exam can have multiple pool questions, potentially from other pools

- pools can be links to other folders (which are no siblings)

- The current folder can be used as well as a pool folder. In this
case, other not-used items can be selected as replacement items
given these match the specified filter characteristics

- Question filtering
* filter by item type:
allow one to select from all/some/some item types
(mc, sc, short text, reordering, composite, ...):
use as replacement items only examples of these types

* filter by minutes and/or points:
use as replacement items only items with matching points/minutes

* filter by language:
use as replacement items only items in a certain language

* Filter per item name pattern:
use as replacement items only items matching a name.
When (short-) names are used systematically, one can e.g.
use the date in the name and specify only items from e.g.
one year ago, via "*2020*", or from some chapter "*ch01", ...
Certainly, it is also possible to use different item
folders for this

Potential further steps:

- Currently, exams containing pool questions are treated as
auto-correctable (which implies automated exam-review (Einsicht), when
from the question pools only question from strictly closed questions
are selected (MC, SC, Ordering). Depending on the detailed settings,
also other item types could be possible (via correct-when), but this
requires a deeper analysis of every question, which is so far not
performed.

- Categorized items: technically, the infrastructure is mostly here to
allow also filtering by categories. This would allow one to select
e.g. from technical questions, case examples, knowledge transfer
questions, research-oriented questions... which are orthogonal to
the filtering currently available. Every lecturer can define
own categories depending on their needs, we could provide
university-wide category-trees, etc. Of course, one could also
define separate pools for these purposes, but categorizing is
probably more convenient and more flexible.

- Performance: when question pools become large (500+ questions) and
the cohorts as well (500+), the current version might require more
tuning. The only critical time is the exam-start, where the random
question placeholders have to be resolved for every student. The
approach from this weekend uses basic caching, but maybe this has to
be extended.

- Protecting selected questions: Question pools are more detached from
an exam than single exercises, a lecturer might have in mind. One
should not allow one to delete questions/question pools when these are
in use. Probably deletion should be a move to a trash-can, which is
actually, an issue for all exams, but getting more important with
pool questions.

- Handling of potential duplicates: When items are pulled from a
question pool, a replacement item is selected by making sure that
this item does not occur already in the query selection. Therefore,
one can safely draw two questions from the same question pool
without fearing that a student gets the same question twice.

This duplicate checking might require some fine-tuning:
* the system checks for duplicates in an exam via POOL/NAME.
* if a lecturer uses two pool-questions in an exam pointing to the same pool,
the systems makes sure, the same question is not used twice.
* however, if a teacher adds a question q1 to pool1 and the same question to pool2,
these two instances have different item ids and are regarded as two different
questions. One could make a test for only checking NAME (without POOL),
but then it might be the case that certain questions are not accepted
although these are different, because they have the same name.

- Statistics: so far, i have not provided any special answer
statistics for treating pool questions.