We supplement these abstract definitions by an in-
tuitive illustration in Graphviz output before a resolu-
tion action is performed, see Figure 2.
The remaining functions implement the product
update rule in a way that goes along the implemen-
tation for the standard product update rule for infor-
mative actions from DEMO (van Eijck, 2004). Most
of the details are standard in DEL and we will skip
them here, there are also some specific details that dif-
fer when questioning actions are considered. Some of
the aspects that emerge when interrogative events are
introduced are studied in (Baltag, 2001). Some other
aspects are even more problematic both conceptually
and technically when multiple questions are consid-
ered, in particular, there is no composition principle
for questions and for complex questioning actions se-
quential or parallel execution lead to different out-
comes. We do not pursue this direction here, a more
detailed discussion of these and other related aspects
can be found in (van Benthem and Minic
˘
a, 2009).
4 APPLICATIONS
This section explores possible applications of results
in previous section. We describe first applications in
teaching and computer supported education and we
also mention some further theoretical developments
towards the end of the section.
A first possible application concerns the role of
question-management actions in interactive educa-
tion. We present ongoing work towards building a
web application with a user-friendly graphical inter-
face linked with Haskell and Graphviz server based
programs in order to produce interactive and intu-
itive visual representations (SVG output) for compu-
tations using questioning actions that are changing
epistemic-issue structures. The workflow diagram for
this application is given in Figure 3. In what follows
we will describe empirical data about the application
as it is at this stage of development. Another possible
application, interdependent on the first, is design and
management of questioning strategies.
The first direction in which we intent to con-
tinue and develop results form previous sections is an
immediate application inside an teaching-supporting
electronic environment. We are aware of previous re-
search in this direction that make the case for the ad-
vantages of having such teaching tools for a variety
of domains and subjects. There is no reason to be-
lieve that the specific domain of logic for interactive
interrogative actions is an exception from this point of
view. Moreover, a suitable teaching environment for
both interactive questioning and abstract issue man-
agement has the potential of producing useful appli-
cations in many other scientific domains. As long as
recurrent interrogative structures are engaged in a spe-
cific field of study, there is good evidence to believe
that a dynamic approach to questioning might be use-
ful for identifying and understanding such patterns.
Some specific aspects of DELQ could make this
task maybe more challenging. For instance, by the
very fact that reasoning about epistemic and interrog-
ative realities is done inside relational structures, an
effective educational environment would have to pro-
vide feedback in both text messages and formulae de-
scribing computations and a more demanding graphi-
cal format. This is still an emerging practice but basic
teaching experience seems to indicate that any type
of feedback that would be relevant and efficient for
teaching purposes should at least contain basic visu-
alizations and processing of graph structures.
Besides allowing to perform model checking in
epistemic structures, DEMO is also designed for pro-
ducing output describing epistemic content of rela-
tional structures in a format that can be graphically
displayed and used to enhance intuitively thrusted
computations about interesting phenomena involving
knowledge and interactive information flow. Given
their very similar relational structure, it is reasonable
to expect that EIM’s are also suitable candidates for
a similar approach. There are also software solutions
that support web-based viewers for Graphviz output.
WebDot is such an example of a scripted service that
could be used for visualizing graphs in HTML docu-
ments to be used as teaching tools.
More concretely, one specific feature of DEMO
is the fact that it can output epistemic models in
Graphviz format. Nodes of the graph represent possi-
ble worlds, edges between nodes represent indistin-
guishability relations, information about the agents
and the valuation is represented by labels on edges
and worlds. For our present purpose, because the
issue relation, used to represend questions, is also
an equivalence relation as is the epistemic indistin-
guishability relation, a representation of both as links
between nodes becomes problematic. In order to re-
flect the conceptual difference between them we de-
cided to use clustering of nodes for questions and
edges for knowledge.
In order to obtain output in the previously spec-
ified graphical format we use the fdp layout pro-
gram. Equivalence classes formed by issue relations
are grouped in one cluster and labels are used to repre-
sent the agents. Figure 2 representa an EIM in which
two agents a and b are ignorant about two proposi-
tions p and q. The initial frame, including all the al-
ternatives, represents a universal issue relation. Ask-
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