<s>
ASN.1	B-Protocol
Information	B-Language
Object	I-Language
Class	I-Language
is	O
a	O
concept	O
widely	O
used	O
in	O
ASN.1	B-Protocol
specifications	O
to	O
address	O
issues	O
related	O
to	O
protocol	O
specification	O
similar	O
to	O
issues	O
addressed	O
by	O
CORBA/IDL	O
specifications	O
.	O
</s>
<s>
Information	O
Object	O
Classes	O
are	O
used	O
for	O
example	O
to	O
specify	O
ROSE	O
(	O
Remote	O
Operations	O
Service	O
Element	O
)	O
protocol	O
in	O
ASN.1	B-Protocol
.	O
</s>
<s>
The	O
simplest	O
way	O
of	O
thinking	O
of	O
ASN.1	B-Protocol
Information	O
Object	O
Classes	O
is	O
to	O
regard	O
them	O
as	O
a	O
way	O
to	O
represent	O
IDL	O
specification	O
in	O
ASN.1	B-Protocol
using	O
concepts	O
derived	O
from	O
the	O
relational	O
databases	O
theory	O
and	O
SQL	B-Language
syntax	O
in	O
particular	O
.	O
</s>
<s>
The	O
concepts	O
used	O
in	O
ASN.1	B-Protocol
are	O
more	O
flexible	O
than	O
the	O
ones	O
used	O
in	O
IDL	O
,	O
because	O
,	O
continuing	O
the	O
analogy	O
,	O
they	O
allow	O
to	O
"	O
customize	O
grammar	O
"	O
of	O
the	O
"	O
IDL	O
specification	O
"	O
.	O
</s>
<s>
ASN.1	B-Protocol
encoding	O
rules	O
are	O
used	O
as	O
a	O
transfer	O
syntax	O
for	O
remote	O
invocations	O
that	O
resemble	O
CORBA/IIOP	O
.	O
</s>
<s>
In	O
the	O
light	O
of	O
this	O
comparison	O
,	O
we	O
can	O
draw	O
an	O
approximate	O
analogy	O
between	O
concepts	O
used	O
in	O
Information	O
Object	O
Classes	O
and	O
SQL	B-Language
and	O
IDL	O
concepts	O
as	O
shown	O
in	O
Table	O
1	O
.	O
</s>
<s>
+Table	O
1	O
:	O
Analogy	O
between	O
concepts	O
in	O
ASN.1	B-Protocol
Information	O
Object	O
Classes	O
,	O
SQL	B-Language
,	O
and	O
IDL	O
ASN.1	B-Protocol
term	O
Analogy	O
in	O
SQL	B-Language
Analogy	O
in	O
IDLInformation	O
Object	O
Class	O
(	O
IOC	O
)	O
SQL	B-Language
table	O
structure	O
descriptor	O
(	O
CREATE	O
TABLE	O
statement	O
)	O
IDL	O
grammar	O
specification	O
(	O
BNF	O
rules	O
)	O
IOC	O
field	O
declarationSQL	O
table	O
column	O
descriptor	O
in	O
CREATE	O
TABLE	O
statement	O
(	O
type	O
of	O
a	O
column	O
)	O
IDL	O
grammar	O
productionInformation	O
Object	O
(	O
IO	O
)	O
SQL	B-Language
table	O
row	O
(	O
INSERT	O
INTO	O
statement	O
)	O
IDL	O
operation	O
declarationIO	O
field	O
definitionCell	O
of	O
SQL	B-Language
table	O
row	O
in	O
INSERT	O
INTO	O
statement	O
(	O
cell	O
value	O
)	O
Portion	O
of	O
IDL	O
operation	O
declaration	O
,	O
typically	O
related	O
to	O
declaration	O
of	O
an	O
operation	O
type	O
code	O
,	O
parameter	O
list	O
,	O
operation	O
return	O
value	O
,	O
or	O
list	O
of	O
exceptionsInformation	O
Object	O
Set	O
(	O
IOS	O
)	O
(	O
collection	O
of	O
Information	O
Objects	O
)	O
Completely	O
defined	O
SQL	B-Language
table	O
(	O
collection	O
of	O
rows	O
)	O
(	O
see	O
Note	O
1	O
)	O
IDL	O
interface	O
definition	O
(	O
collection	O
of	O
operations	O
)	O
ASN.1	B-Protocol
data	O
type	O
using	O
references	O
to	O
IOC	O
fields	O
parameterized	O
with	O
IOS	O
(	O
typically	O
a	O
collection	O
of	O
semantically	O
related	O
types	O
designating	O
request	O
,	O
response	O
,	O
and	O
exception	O
,	O
all	O
parameterized	O
with	O
the	O
same	O
IOS	O
)	O
-High-level	O
format	O
(	O
grammar	O
specification	O
)	O
of	O
a	O
frame	O
(	O
marshalling	O
buffer	O
)	O
carrying	O
CORBA	B-Architecture
request	O
,	O
response	O
,	O
or	O
exceptionASN.1	O
encoding	O
rules	O
and	O
transfer	O
syntaxes	O
(	O
BER	O
,	O
PER	O
)	O
-Low-level	O
encoding	O
of	O
requests	O
,	O
responses	O
and	O
exception	O
indicators	O
suitable	O
for	O
physical	O
transfer	O
over	O
the	O
mediumNote	O
1	O
.	O
</s>
<s>
The	O
analogy	O
between	O
IOS	O
and	O
an	O
SQL	B-Language
table	O
is	O
not	O
quite	O
correct	O
.	O
</s>
<s>
SQL	B-Language
permits	O
only	O
one	O
instance	O
of	O
a	O
table	O
of	O
given	O
type	O
(	O
OPERATION	O
in	O
the	O
example	O
below	O
)	O
,	O
while	O
ASN.1	B-Protocol
permits	O
multiple	O
Information	O
Object	O
Sets	O
derived	O
from	O
the	O
same	O
Information	B-Language
Object	I-Language
Class	I-Language
,	O
what	O
should	O
be	O
most	O
correctly	O
related	O
to	O
multiple	O
instances	O
of	O
the	O
same	O
table	O
in	O
terms	O
of	O
SQL	B-Language
(	O
OPERATION	O
in	O
the	O
example	O
below	O
)	O
.	O
</s>
<s>
Table	O
2	O
illustrates	O
by	O
example	O
correspondence	O
of	O
ASN.1	B-Protocol
concepts	O
to	O
similar	O
constructs	O
found	O
in	O
SQL	B-Language
and	O
IDL	O
.	O
</s>
<s>
)	O
-High-level	O
format	O
of	O
a	O
frame	O
carrying	O
CORBA	B-Architecture
request	O
,	O
response	O
,	O
or	O
exception.BER	O
,	O
PER	O
etc.0110	O
0111	O
0010	O
110	O
...	O
encoding	O
of	O
requests	O
,	O
responses	O
and	O
exception	O
indicators.Note	O
1	O
.	O
</s>
<s>
The	O
type_info	O
and	O
ref_to_table	O
SQL	B-Language
data	O
types	O
are	O
imaginary	O
data	O
types	O
.	O
</s>
<s>
They	O
do	O
not	O
exist	O
in	O
SQL	B-Language
and	O
they	O
were	O
introduced	O
artificially	O
to	O
help	O
better	O
explain	O
ASN.1	B-Protocol
concepts	O
.	O
</s>
<s>
The	O
type_info	O
data	O
type	O
means	O
that	O
its	O
value	O
is	O
a	O
reference	O
to	O
an	O
ASN.1	B-Protocol
type	O
.	O
</s>
<s>
The	O
ref_to_table	O
data	O
type	O
means	O
that	O
its	O
value	O
is	O
a	O
reference	O
to	O
another	O
instance	O
of	O
SQL	B-Language
table	O
(	O
ERROR	O
table	O
in	O
this	O
case	O
)	O
.	O
</s>
<s>
While	O
we	O
know	O
that	O
in	O
real	O
SQL	B-Language
we	O
ca	O
n't	O
have	O
multiple	O
instances	O
of	O
the	O
same	O
table	O
,	O
let	O
's	O
imagine	O
for	O
the	O
purposes	O
of	O
accuracy	O
of	O
our	O
description	O
that	O
we	O
actually	O
can	O
.	O
</s>
<s>
In	O
SQL	B-Language
terms	O
,	O
the	O
combination	O
of	O
types	O
and	O
values	O
forming	O
a	O
legal	O
instance	O
of	O
that	O
type	O
shall	O
belong	O
to	O
a	O
single	O
row	O
of	O
a	O
table	O
.	O
</s>
<s>
The	O
example	O
specification	O
of	O
ASN.1	B-Protocol
data	O
types	O
does	O
not	O
define	O
any	O
formal	O
correspondence	O
between	O
Request	O
,	O
Response	O
,	O
and	O
Exception	O
types	O
,	O
event	O
though	O
the	O
OPERATION	O
Information	B-Language
Object	I-Language
Class	I-Language
used	O
in	O
all	O
three	O
types	O
defines	O
a	O
semantic-level	O
correlation	O
between	O
request	O
,	O
response	O
,	O
and	O
possible	O
error	O
conditions	O
,	O
while	O
IDL	O
operation	O
definition	O
does	O
so	O
formally	O
.	O
</s>
<s>
Unlike	O
IDL	O
operation	O
definition	O
,	O
the	O
correspondence	O
between	O
frames	O
is	O
non-binding	O
and	O
is	O
purely	O
semantical	O
,	O
although	O
it	O
can	O
be	O
exploited	O
by	O
an	O
ASN.1	B-Protocol
tool	O
in	O
a	O
tool-specific	O
fashion	O
.	O
</s>
<s>
If	O
you	O
carefully	O
examine	O
the	O
ASN.1	B-Protocol
example	O
presented	O
in	O
Table	O
2	O
and	O
compare	O
it	O
to	O
IDL	O
concepts	O
,	O
you	O
will	O
see	O
one	O
important	O
limitation	O
on	O
the	O
ASN.1	B-Protocol
side	O
.	O
</s>
<s>
Our	O
example	O
ASN.1	B-Protocol
data	O
types	O
which	O
we	O
agreed	O
to	O
compare	O
to	O
a	O
high-level	O
CORBA/IDL	O
transfer	O
syntax	O
specification	O
are	O
limited	O
to	O
definition	O
of	O
such	O
transfer	O
syntax	O
only	O
for	O
a	O
single	O
instance	O
of	O
what	O
we	O
compared	O
to	O
an	O
IDL	O
interface	O
(	O
Information	O
Object	O
Set	O
in	O
ASN.1	B-Protocol
terms	O
)	O
.	O
</s>
<s>
With	O
the	O
current	O
set	O
of	O
known	O
tools	O
you	O
ca	O
n't	O
define	O
such	O
a	O
transfer	O
syntax	O
in	O
a	O
generic	O
way	O
in	O
,	O
say	O
,	O
ASN.1	B-Protocol
specification	O
A	O
and	O
then	O
reuse	O
it	O
in	O
ASN.1	B-Protocol
specifications	O
B	O
and	O
C	O
that	O
define	O
concrete	O
application-specific	O
"	O
IDL	O
interfaces	O
"	O
on	O
which	O
A	O
does	O
not	O
depend	O
.	O
</s>
<s>
The	O
reason	O
for	O
the	O
current	O
limitation	O
is	O
that	O
we	O
currently	O
hard-code	O
our	O
Information	O
Object	O
Set	O
(	O
MyWarehouseOps	O
in	O
case	O
of	O
OPERATION	O
,	O
or	O
MyErrorSet	O
in	O
case	O
of	O
ERROR	O
)	O
into	O
our	O
ASN.1	B-Protocol
data	O
types	O
(	O
high-level	O
transfer	O
syntax	O
specification	O
)	O
.	O
</s>
<s>
Now	O
the	O
high-level	O
transfer	O
syntax	O
descriptor	O
Request	O
can	O
be	O
parameterized	O
with	O
any	O
arbitrary	O
Information	O
Object	O
Set	O
(	O
"	O
IDL	O
interface	O
"	O
)	O
conforming	O
to	O
the	O
Information	B-Language
Object	I-Language
Class	I-Language
specification	O
(	O
"	O
IDL	O
grammar	O
"	O
)	O
.	O
</s>
<s>
Tokens	O
all	O
in	O
capital	O
mean	O
keywords	O
,	O
tokens	O
starting	O
with	O
&	O
mean	O
productions	O
requiring	O
substitution	O
of	O
the	O
corresponding	O
entity	O
in	O
place	O
of	O
the	O
token	O
(	O
ASN.1	B-Protocol
value	O
,	O
type	O
,	O
or	O
Information	O
Object	O
Set	O
,	O
either	O
instance	O
or	O
reference	O
thereof	O
)	O
,	O
depending	O
on	O
the	O
Information	B-Language
Object	I-Language
Class	I-Language
to	O
which	O
this	O
field	O
refers	O
.	O
</s>
<s>
To	O
fully	O
understand	O
the	O
grammar	O
concept	O
behind	O
the	O
WITH	O
SYNTAX	O
clause	O
,	O
imagine	O
we	O
wrote	O
our	O
OPERATION	O
Information	B-Language
Object	I-Language
Class	I-Language
definition	O
as	O
follows	O
:	O
</s>
