<s>
PRTV	B-Application
(	O
Peterlee	O
Relational	O
Test	O
Vehicle	O
)	O
was	O
the	O
world	O
's	O
first	O
relational	B-Application
database	I-Application
management	I-Application
system	I-Application
that	O
could	O
handle	O
significant	O
data	O
volumes	O
.	O
</s>
<s>
PRTV	B-Application
was	O
a	O
successor	O
from	O
the	O
very	O
first	O
relational	O
implementation	O
,	O
IS1	B-Application
.	O
</s>
<s>
PRTV	B-Application
included	O
several	O
firsts	O
in	O
the	O
relational	O
database	O
area	O
:	O
</s>
<s>
PRTV	B-Application
was	O
based	O
on	O
a	O
relational	O
algebra	O
,	O
Information	O
Systems	O
Base	O
Language	O
(	O
ISBL	O
)	O
and	O
followed	O
the	O
relational	O
model	O
very	O
strictly	O
.	O
</s>
<s>
Even	O
features	O
such	O
as	O
user-defined	B-Language
functions	I-Language
were	O
formalized	O
within	O
that	O
model	O
.	O
</s>
<s>
The	O
PRTV	B-Application
team	O
also	O
introduced	O
surrogates	O
to	O
the	O
relational	O
model	O
to	O
help	O
formalize	O
relational	O
update	O
operations	O
;	O
and	O
a	O
formalisation	O
for	O
updating	O
through	O
views	O
.	O
</s>
<s>
However	O
neither	O
of	O
these	O
was	O
implemented	O
within	O
PRTV	B-Application
.	O
</s>
<s>
PRTV	B-Application
emphatically	O
did	O
not	O
implement	O
NULL	O
values	O
,	O
because	O
this	O
conception	O
was	O
introduced	O
only	O
in	O
1979	O
.	O
</s>
<s>
PRTV	B-Application
was	O
itself	O
never	O
available	O
as	O
a	O
product	O
,	O
but	O
the	O
Urban	O
Management	O
System	O
built	O
on	O
it	O
was	O
available	O
as	O
a	O
limited	O
IBM	O
product	O
.	O
</s>
<s>
PRTV	B-Application
was	O
written	O
in	O
a	O
mixture	O
of	O
languages	O
.	O
</s>
<s>
MP/3	O
was	O
a	O
macro	O
processing	O
language	O
developed	O
at	O
Peterlee	O
from	O
1973	O
onwards	O
,	O
similar	O
to	O
ML/I	B-Language
or	O
TRAC	B-Language
.	O
</s>
<s>
PRTV	B-Application
ran	O
on	O
System/370	O
IBM	O
mainframes	O
.	O
</s>
