<s>
The	O
UB-tree	B-Data_Structure
as	O
proposed	O
by	O
Rudolf	O
Bayer	O
and	O
Volker	O
Markl	O
is	O
a	O
balanced	B-Data_Structure
tree	I-Data_Structure
for	O
storing	O
and	O
efficiently	O
retrieving	O
multidimensional	B-Algorithm
data	I-Algorithm
.	O
</s>
<s>
It	O
is	O
basically	O
a	O
B+	O
tree	O
(	O
information	O
only	O
in	O
the	O
leaves	O
)	O
with	O
records	O
stored	O
according	O
to	O
Z-order	B-Algorithm
,	O
also	O
called	O
Morton	B-Algorithm
order	I-Algorithm
.	O
</s>
<s>
Z-order	B-Algorithm
is	O
simply	O
calculated	O
by	O
bitwise	O
interlacing	O
the	O
keys	O
.	O
</s>
<s>
A	O
solution	O
to	O
this	O
"	O
crucial	O
part	O
of	O
the	O
UB-tree	B-Data_Structure
range	O
query	O
"	O
linear	O
with	O
the	O
z-address	O
bit	O
length	O
has	O
been	O
described	O
later	O
.	O
</s>
<s>
This	O
method	O
has	O
already	O
been	O
described	O
in	O
an	O
older	O
paper	O
where	O
using	O
Z-order	B-Algorithm
with	O
search	O
trees	O
has	O
first	O
been	O
proposed	O
.	O
</s>
