Information Technology Reference
In-Depth Information
peated on the parent node. It must be noted that
the evaluations at the parent node have to be per-
formed against the result of modifying the environ-
ment π of the student with the set of actions on the
corresponding exit edge (see Figure 3).
If the transition leads to a container node, a
new environment π is created, its set of initializa-
tion actions I is executed modifying π, and the
next activity to be delivered is one of its entry
nodes. If the node selected is itself an entry node,
this entry node selection procedure is repeated.
It must be noted that, although several changes
of hierarchy level may be involved in a transition,
one and only one horizontal edge (i.e. not exit) is
always followed.
It can be the case that no transition is available.
That means that the graph is not correctly designed.
The algorithm is not specified for such a case: the
behavior of the system is left to the application.
This algorithm provides a powerful and in-
tuitive framework to organize a large number of
learning units, and at the same time, characterize
multiple sequences of these units. This power
is obtained because the sequencing decisions
are hierarchically specified. When designing a
sequencing graph, an author may focus on the
low level decisions on how to sequence a set of
learning units depending on the results obtained
so far by a student. At the same time, once these
sequences have been specified for several topics,
the sequencing of such topics can be done by
considering them as atomic units and, therefore,
be reused in another graph. This improves reus-
ability, which is one of our four goals.
Entry Nodes, Exit Nodes and
the Inter-Level Interface
The existence of output edges is necessary be-
cause it allows data from lower level graphs to
be exported to higher levels. That is the way in
which the inter-level interface is designed: it al-
Figure 3. Function find_transitions
Search WWH ::




Custom Search