<s>
In	O
the	O
exchange	O
of	O
information	O
over	O
a	O
communication	O
channel	O
,	O
an	O
out-of-band	B-Protocol
agreement	I-Protocol
is	O
an	O
agreement	O
or	O
understanding	O
between	O
the	O
communicating	O
parties	O
that	O
is	O
not	O
included	O
in	O
any	O
message	O
sent	O
over	O
the	O
channel	O
but	O
which	O
is	O
relevant	O
for	O
the	O
interpretation	O
of	O
such	O
messages	O
.	O
</s>
<s>
By	O
extension	O
,	O
in	O
a	O
client	B-Operating_System
–	I-Operating_System
server	I-Operating_System
or	O
provider-requester	O
setting	O
,	O
an	O
out-of-band	B-Protocol
agreement	I-Protocol
is	O
an	O
agreement	O
or	O
understanding	O
that	O
governs	O
the	O
semantics	B-Application
of	O
the	O
request/response	O
interface	O
but	O
which	O
is	O
not	O
part	O
of	O
the	O
formal	O
or	O
contractual	O
description	O
of	O
the	O
interface	O
specification	O
itself	O
.	O
</s>
