A *(user interface) *(term) for a representation of some group of information that at least partially makes use of structural or symbolic representation. The study of diagrams has become particularly interesting in recent years, and programmatic generation of them is in _("TUNES' interface generation's"| http://tunes.org/Interfaces/ingen.html) interest.

<ul class="links">
<li>_(Diagrammatic Representation And Reasoning| http://citeseer.nj.nec.com/kulpa94diagrammatic.html), a paper given in 1994 as an overview of the subject.
<li>_(The entry on diagrams| http://plato.stanford.edu/entries/diagrams/) from the Stanford Encyclopedia of Philosophy.
<li>_(A Meta-Taxonomy for Diagram Research| http://www.cl.cam.ac.uk/users/afb21/publications/yuri-chapter.html), a recent chapter (by _("Alan Blackwell"|http://www.cl.cam.ac.uk/users/afb21/), who has written many other _(HCI) papers and is the mantainer of <em>Cognitive Dimensions of Notations
Resource Site</em>, see _(Psychology of Programming)) of the following book.
<li>_(Diagrammatic Representation And Reasoning| http://www.springer.de/cgi-bin/search_book.pl?isbn=1-85233-242-5&cookie=done), a Springer-Verlag book in 2002 which covers many details in greater depth of analysis, by
     _("Bernd Meyer"|http://welcome.to/bernd.meyer/),
_("Michael Anderson"|http://www.cs.hartford.edu/~anderson/personal/) and
 _("Patrick Olivier"|http://www-users.cs.york.ac.uk/~patrick/).
<li>_("ACTING WITH DIAGRAMS: how to plan strategies"|http://name.math.univ-rennes1.fr/nathalie.rittemard/twd98_intro.html).
<li>_("Diagrammatic Reasoning Site"|http://www.cs.hartford.edu/~anderson/).  
<li>_("E.R. Tufte"|http://www.edwardtufte.com/tufte/)'s books on information design are also quite relevant.
<li>_("International Conference on the Theory and Application of Diagrams"|http://www.hcirn.com/res/event/diagrams.php).
<li>_("Diagrammatic Reasoning and Knowledge Acquisition"|http://www.psychology.nottingham.ac.uk/staff/Peter.Cheng/DRandKA/).
<li>_("Thinking With Diagrams"|http://www.wideman-one.com/gw/xm/concmod/thinkwdiag.htm).
<li>_("Diagramming"|http://ilex.cc.kcl.ac.uk/wlm/diagram/).
</ul>

In _(category theory) a diagram is a graph where edges are labelled with _(morphisms|morphism) and vertices are labelled with objects, in a way that typing of morphisms is respected. Formally, a diagram in a category C is a functor from the free category generated by the graph to C. A commutative diagram is a diagram where some equation holds. The formal definition is the same, where the free category is suitably quotiented by the _(congruence) induced by the equations.
