  The work in the paper presents an animation extension ($CHR^{vis}$) to
Constraint Handling Rules (CHR). Visualizations have always helped programmers
understand data and debug programs. A picture is worth a thousand words. It can
help identify where a problem is or show how something works. It can even
illustrate a relation that was not clear otherwise. $CHR^{vis}$ aims at
embedding animation and visualization features into CHR programs. It thus
enables users, while executing programs, to have such executions animated. The
paper aims at providing the operational semantics for $CHR^{vis}$. The
correctness of $CHR^{vis}$ programs is also discussed. Some applications of the
new extension are also introduced.
