Single Enumeration Tree
abcd
{ }
r1r2r3r4
{ }
abc
{r1}
r1r2r3
{c}
r1r2
{ac}
ab
{r1}
abd { }
r1r2r4 { }
a
{r1r2}
ac
{r1r2}
acd { r2}
r1
{abc}
r1r3
{bc}
r1r3r4 { }
ad {r2}
r1r4 { }
bc
{r1r3}
r2r3r4 { }
bcd
{ }
r2r3
{c}
{ }
b
{r1r3}
r2
{acd}
{ }
r2r4{d }
bd { }
c
{r1r2r3}
cd
{r2 }
r3r4
{ }
r3
{bc}
d
{r2r4}
r4{d}
Feature enumeration
Row enumeration