<s>
PAD	O
or	O
Portable	B-Language
Application	I-Language
Description	I-Language
is	O
a	O
machine-readable	O
document	O
format	O
and	O
specification	O
designed	O
by	O
the	O
Association	O
of	O
Software	O
Professionals	O
and	O
introduced	O
in	O
1998	O
.	O
</s>
<s>
PAD	O
allows	O
software	O
authors	O
to	O
provide	O
standardized	O
product	O
descriptions	O
and	O
specifications	O
to	O
online	O
sources	O
in	O
a	O
standard	O
way	O
,	O
using	O
a	O
simple	O
XML	B-Language
schema	I-Language
that	O
allows	O
webmasters	O
and	O
program	O
librarians	O
to	O
automate	O
new	O
program	O
listings	O
and	O
update	O
existing	O
listings	O
in	O
their	O
catalog	O
.	O
</s>
<s>
PAD	B-Language
files	I-Language
most	O
commonly	O
have	O
.XML	O
or	O
.PAD	O
file	O
name	O
extension	O
.	O
</s>
<s>
If	O
multiple	O
languages	O
are	O
represented	O
in	O
a	O
single	O
PAD	B-Language
file	I-Language
,	O
then	O
correct	O
parsing	O
does	O
require	O
descending	O
through	O
the	O
tag	O
path	O
because	O
leaf	O
tags	O
are	O
duplicated	O
for	O
each	O
language	O
supported	O
.	O
</s>
<s>
Each	O
field	O
in	O
the	O
specification	O
has	O
a	O
regular	B-Language
expression	I-Language
associated	O
with	O
it	O
.	O
</s>
<s>
The	O
regular	B-Language
expression	I-Language
acts	O
as	O
a	O
constraint	O
on	O
the	O
field	O
:	O
if	O
it	O
matches	O
,	O
the	O
field	O
value	O
is	O
legal	O
and	O
if	O
it	O
fails	O
to	O
match	O
,	O
the	O
field	O
and	O
the	O
PAD	B-Language
file	I-Language
as	O
a	O
whole	O
do	O
not	O
conform	O
to	O
specification	O
.	O
</s>
<s>
Only	O
files	O
where	O
all	O
fields	O
in	O
the	O
file	O
pass	O
validation	O
are	O
properly	O
called	O
PAD	B-Language
files	I-Language
.	O
</s>
<s>
AppVisor	O
allows	O
publishers	O
to	O
upgrade	O
their	O
v3.1	O
PAD	B-Language
files	I-Language
to	O
v4.0	O
.	O
</s>
<s>
However	O
,	O
the	O
generated	O
PAD	B-Language
file	I-Language
cannot	O
be	O
exported	O
but	O
only	O
submitted	O
directly	O
to	O
some	O
directories	O
.	O
</s>
