<s>
In	O
mathematics	O
,	O
a	O
summation	B-Algorithm
equation	I-Algorithm
or	O
discrete	B-Algorithm
integral	I-Algorithm
equation	I-Algorithm
is	O
an	O
equation	O
in	O
which	O
an	O
unknown	O
function	O
appears	O
under	O
a	O
summation	O
sign	O
.	O
</s>
<s>
The	O
theories	O
of	O
summation	B-Algorithm
equations	I-Algorithm
and	O
integral	B-Algorithm
equations	I-Algorithm
can	O
be	O
unified	O
as	O
integral	B-Algorithm
equations	I-Algorithm
on	O
time	O
scales	O
using	O
time	O
scale	O
calculus	O
.	O
</s>
<s>
A	O
summation	B-Algorithm
equation	I-Algorithm
compares	O
to	O
a	O
difference	O
equation	O
as	O
an	O
integral	B-Algorithm
equation	I-Algorithm
compares	O
to	O
a	O
differential	O
equation	O
.	O
</s>
<s>
The	O
Volterra	O
summation	B-Algorithm
equation	I-Algorithm
is	O
:	O
</s>
