Situation

Testing in Mathematics and other nature sciences requires test question types that support calculation, formulas and equations. Neither simple multiple choice questions nor formula questions can fulfill this requirement because these question types only check the given answer against a predefined set of numbers and characters. They are not calculating the result and accepting different submissions with the same value, e.g. 2 and 4/2.

Possible Solution

A question type that checks the given answer by using a Computer Algebra System (CAS) would solve this problem and allow to offer valuble and helpful test&assessments to students.
 
A well matured and proven use case for a CAS connection is STACK which offers a connection to the popular MAXIMA CAS. A STACK plugin is already available for Moodle and often used. It would be a reasonable approach to adopt the Moodle plugin for STACK and port it to ILIAS. But this requires to get off all Moodle specific code out of the plugin and to transform it to a ILIAS compatible plugin.
 
For the implementation we need to distinguish between the learner view and the author's side of the question editor. While the presentation of a CAS question only needs to deliver a connection to the CAS which is hosted somewhere, the authoring side of creating a CAS question is different and much more challeging.

Learner View

The learner's view needs only to support the CAS connection and deliver the input given by the learner to the CAS. The result processed by the CAS is send back to ILIAS and determines the result of the answer. According to the result points are given to the user for this answer.

Workaround for a first implementation
 
Facing the situation that a full funding of the CAS question type cannot be offered immediately, a two-step solution seems to be a reasonable strategy to implement the feature as soon as possible:
 
In a first step only the learner's view of this question type is implemented while the editing of the question still takes place in a STACK plugin embedded in Moodle. STACK questions created by Moodle are exported and transformed to ILIAS compatible question types that can easily be imported. Such CAS questions can become part of a test question pool in ILIAS.

The following sub tasks are needed to develop an ILIAS plugin for the Learner View of STACK questions:

1. Technical conception of the plugin and coordination with the developers of the original STACK question type (to ensure that platform specific and independent parts can be separately developed in the future)
2. Development of the plugins basic architecture and the data structures to save the definition of stack question
3. Development of the technical interface to the platform independent part of STACK (if needed, with wrappers for current moodle specific classes and function calls)
4. Development of a conversion for exported questions from STACK in moddle to STACK in ILIAS (single question and question pools)
5. Conception of the user interface for the Learner View: preview, execution, result ans print view of STACK questions result and print view
6. Implementation of the user interface for the Learner View

Authoring Environment

In a second step the authoring environment of such a CAS question type has to be implemented as a plugin for the question type plugin slot. Such an authoring interface needs to offer all options for defining a CAS question.

Discussion

Matthias Kunkel, 20 Mar 2014: A first prototype of the learner interface will be presented end of March on the team meeting of optes project in Detmold. An additional presentation is planned for the DevConf at March 27 in Münster. The development of the authoring interface starts end of April and is currently scheduled until July/August.

Implementation

Matthias Kunkel, August 08, 2014: A first stable version of the question plugin has already been published, see http://www.ilias.de/docu/goto_docu_dcl_3342_358.html. It allows to import STACK questions developed in Moodle and to run them in ILIAS tests.

Fred Neumann, February 06, 2015: version 2 (beta) with an authoring interface is now available, see http://www.ilias.de/docu/goto_docu_cat_4119.html.

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