A Logic Task
Problem Instance
Consider the following problem:
This problem has two steps:
- Prove that mr. Alfie wears glasses, or that he wears not.
- Write the answer.
Student Interaction
- The main task Logic_Problem 456.
This contains the problem statement and issues the challange.
It has a has a panel where the student can
state his answer. This tool is only available
after the proof subtask has been successfully completed.
An applet showing many of this task features
can be seen here.
- The subtask proof.
In this subtask the student can make logic inferences
from the assumptions. First, he has to write a statement
using a propositions' editor. Afterwards, he must
explain that statement by choosing the premisses on which the
conclusion is based. When the inference is submited,
the task evaluates it, and, if found wrong,
a message is sent to the student giving
a counter-example, and explaining why
the inference is not valid.
Construction
This task has a single parameter to
be instanciated, of type
PROPOSITIONAL_CALCULUS_PROBLEM.
A term object of this type consists of:
- A short textual description of the context:
"The follwing statements refer to a three friends universe."
- A set of formal propositional expressions (the problem assumptions)
- A meaning to the involved terms and predicates:
| Symbol | Meaning |
| a | mr. Alfie |
| b | mr. Been |
| c | mr. Charlie |
| G(x) | x has glasses |
| T(x) | x has teeth |
- A goal proposition: G(a).
- The challenge description:
"From these assumptions, investigate if mr. Alfie wears glasses."
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