<s>
A	O
content	B-Device
reference	I-Device
identifier	I-Device
or	O
CRID	B-Device
is	O
a	O
concept	O
from	O
the	O
standardization	O
work	O
done	O
by	O
the	O
TV-Anytime	B-Device
forum	O
.	O
</s>
<s>
The	O
concept	O
of	O
CRID	B-Device
permits	O
referencing	O
contents	O
unambiguously	O
,	O
regardless	O
of	O
their	O
location	O
,	O
i.e.	O
,	O
without	O
knowing	O
specific	O
broadcast	B-Operating_System
information	O
(	O
time	O
,	O
date	O
and	O
channel	O
)	O
or	O
how	O
to	O
obtain	O
them	O
through	O
a	O
network	O
,	O
for	O
instance	O
,	O
by	O
means	O
of	O
a	O
streaming	O
service	O
or	O
by	O
downloading	O
a	O
file	O
from	O
an	O
Internet	O
server	O
.	O
</s>
<s>
This	O
framework	O
allows	O
for	O
the	O
separation	O
between	O
the	O
reference	O
to	O
a	O
given	O
content	O
(	O
the	O
CRID	B-Device
)	O
and	O
the	O
necessary	O
information	O
to	O
acquire	O
it	O
,	O
which	O
is	O
called	O
a	O
“	O
locator	O
”	O
.	O
</s>
<s>
Each	O
CRID	B-Device
may	O
lead	O
to	O
one	O
or	O
more	O
locators	O
which	O
will	O
represent	O
different	O
copies	O
of	O
the	O
same	O
content	O
.	O
</s>
<s>
They	O
may	O
be	O
identical	O
copies	O
broadcast	B-Operating_System
in	O
different	O
channels	O
or	O
dates	O
,	O
or	O
cost	O
different	O
prices	O
.	O
</s>
<s>
It	O
may	O
also	O
be	O
the	O
case	O
that	O
the	O
resolution	O
process	O
of	O
a	O
CRID	B-Device
provides	O
another	O
CRID	B-Device
as	O
a	O
result	O
(	O
for	O
example	O
,	O
its	O
reference	O
in	O
a	O
different	O
network	O
,	O
where	O
it	O
has	O
an	O
alternative	O
identifier	O
assigned	O
by	O
a	O
different	O
operator	O
)	O
or	O
a	O
set	O
of	O
CRIDs	B-Device
(	O
for	O
instance	O
,	O
if	O
the	O
original	O
CRID	B-Device
represents	O
a	O
TV	O
series	O
,	O
in	O
which	O
case	O
the	O
resolution	O
process	O
would	O
result	O
in	O
the	O
list	O
of	O
CRIDs	B-Device
representing	O
each	O
episode	O
)	O
.	O
</s>
<s>
From	O
the	O
above	O
it	O
can	O
be	O
concluded	O
that	O
provided	O
that	O
a	O
given	O
content	O
can	O
belong	O
to	O
many	O
groups	O
(	O
each	O
possibly	O
defined	O
by	O
distinctive	O
qualities	O
)	O
,	O
it	O
is	O
possible	O
that	O
many	O
CRIDs	B-Device
carry	O
the	O
same	O
content	O
.	O
</s>
<s>
That	O
is	O
,	O
several	O
CRIDs	B-Device
may	O
be	O
resolved	O
into	O
the	O
same	O
locator	O
.	O
</s>
<s>
A	O
CRID	B-Device
is	O
not	O
exactly	O
a	O
universal	O
,	O
unique	O
and	O
exclusive	O
identifier	O
for	O
a	O
given	O
content	O
.	O
</s>
<s>
It	O
is	O
closely	O
related	O
to	O
the	O
authority	O
that	O
creates	O
it	O
,	O
to	O
the	O
resolution	O
service	O
provider	O
,	O
and	O
to	O
the	O
content	O
provider	O
in	O
such	O
a	O
way	O
that	O
the	O
same	O
content	O
may	O
have	O
different	O
CRIDs	B-Device
depending	O
on	O
the	O
field	O
in	O
which	O
they	O
are	O
used	O
(	O
for	O
example	O
,	O
a	O
different	O
one	O
for	O
each	O
television	O
operator	O
that	O
has	O
the	O
rights	O
to	O
broadcast	B-Operating_System
the	O
content	O
)	O
.	O
</s>
<s>
A	O
CRID	B-Device
is	O
specified	O
much	O
like	O
URLs	O
.	O
</s>
<s>
In	O
fact	O
,	O
a	O
CRID	B-Device
is	O
a	O
so-called	O
URI	B-Protocol
.	O
</s>
<s>
Typically	O
,	O
the	O
content	O
creator	O
,	O
the	O
broadcaster	O
or	O
a	O
third	O
party	O
will	O
use	O
their	O
DNS-names	O
in	O
a	O
combination	O
with	O
a	O
product-specific	O
name	O
to	O
create	O
globally	O
unique	O
CRIDs	B-Device
.	O
</s>
<s>
That	O
is	O
,	O
the	O
syntax	O
of	O
a	O
CRID	B-Device
is	O
:	O
</s>
<s>
The	O
authority	O
field	O
represents	O
the	O
entity	O
that	O
created	O
the	O
CRID	B-Device
and	O
its	O
format	O
is	O
that	O
of	O
a	O
DNS	B-Protocol
name	I-Protocol
.	O
</s>
<s>
As	O
an	O
example	O
,	O
let	O
's	O
assume	O
that	O
BBC	O
wanted	O
to	O
make	O
a	O
CRID	B-Device
for	O
(	O
all	O
the	O
programs	O
of	O
)	O
the	O
Olympics	O
in	O
China	O
.	O
</s>
<s>
This	O
would	O
be	O
a	O
group	O
CRID	B-Device
,	O
that	O
is	O
,	O
a	O
CRID	B-Device
representing	O
a	O
group	O
of	O
contents	O
.	O
</s>
<s>
Currently	O
,	O
four	O
types	O
of	O
CRIDs	B-Device
are	O
playing	O
a	O
major	O
role	O
in	O
some	O
unidirectional	B-Device
television	O
networks	O
:	O
programme	O
CRID	B-Device
,	O
series	O
CRID	B-Device
,	O
group	O
CRID	B-Device
,	O
and	O
recommendation	O
CRID	B-Device
.	O
</s>
<s>
One	O
of	O
the	O
most	O
important	O
applications	O
of	O
CRIDs	B-Device
is	O
the	O
so-called	O
series	O
link	O
recording	O
function	O
(	O
SL	O
)	O
of	O
modern	O
digital	B-Application
video	I-Application
recorders	I-Application
(	O
DVR	B-Application
,	O
PVR	B-Application
)	O
.	O
</s>
<s>
The	O
locators	O
 '	O
format	O
,	O
as	O
established	O
in	O
TV-Anytime	B-Device
,	O
is	O
quite	O
generic	O
and	O
simple	O
,	O
and	O
corresponds	O
to	O
:	O
</s>
<s>
The	O
location	O
resolution	O
process	O
is	O
the	O
procedure	O
by	O
which	O
,	O
starting	O
from	O
the	O
CRID	B-Device
of	O
a	O
given	O
content	O
,	O
one	O
or	O
several	O
locators	O
of	O
that	O
content	O
are	O
obtained	O
.	O
</s>
<s>
Resolving	O
a	O
CRID	B-Device
can	O
be	O
a	O
direct	O
process	O
,	O
which	O
leads	O
immediately	O
to	O
one	O
or	O
many	O
locators	O
,	O
or	O
it	O
may	O
also	O
happen	O
that	O
in	O
the	O
first	O
place	O
one	O
or	O
many	O
intermediate	O
CRIDs	B-Device
are	O
returned	O
,	O
which	O
must	O
undergo	O
the	O
same	O
procedure	O
to	O
finally	O
obtain	O
one	O
or	O
several	O
locators	O
.	O
</s>
<s>
Consulting	O
them	O
repeatedly	O
will	O
take	O
the	O
receiver	O
from	O
a	O
CRID	B-Device
to	O
one	O
or	O
many	O
locators	O
that	O
will	O
allow	O
it	O
to	O
acquire	O
the	O
content	O
.	O
</s>
<s>
The	O
RAR	O
table	O
is	O
one	O
or	O
many	O
data	O
structures	O
that	O
provide	O
the	O
receiver	O
,	O
for	O
each	O
authority	O
that	O
submits	O
CRIDs	B-Device
,	O
information	O
on	O
the	O
corresponding	O
resolution	O
service	O
provider	O
.	O
</s>
<s>
Among	O
other	O
things	O
,	O
it	O
informs	O
about	O
which	O
mechanism	O
is	O
used	O
to	O
provide	O
information	O
to	O
resolve	O
the	O
CRIDs	B-Device
from	O
each	O
authority	O
.	O
</s>
<s>
That	O
is	O
,	O
one	O
or	O
many	O
RAR	O
records	O
must	O
exist	O
for	O
each	O
authority	O
that	O
indicate	O
the	O
receiver	O
where	O
it	O
has	O
to	O
go	O
to	O
resolve	O
the	O
CRIDs	B-Device
of	O
that	O
particular	O
authority	O
.	O
</s>
<s>
For	O
example	O
,	O
in	O
the	O
record	O
of	O
the	O
figure	O
(	O
expressed	O
by	O
means	O
of	O
a	O
XML	O
structure	O
,	O
according	O
to	O
the	O
XML	O
Schema	O
defined	O
in	O
the	O
TV-Anytime	B-Device
)	O
there	O
is	O
an	O
authority	O
called	O
“	O
tve.es”	O
,	O
whose	O
resolution	O
service	O
provider	O
is	O
the	O
entity	O
“	O
rtve.es”	O
,	O
available	O
on	O
the	O
URL	O
"	O
http://tva.rtve.es/locres/tve	O
"	O
,	O
which	O
means	O
there	O
is	O
resolution	O
information	O
in	O
that	O
URL	O
.	O
</s>
<s>
These	O
RAR	O
records	O
will	O
have	O
reached	O
the	O
receiver	O
in	O
an	O
indefinite	O
form	O
,	O
unimportant	O
for	O
the	O
TV-Anytime	B-Device
specification	O
,	O
which	O
will	O
depend	O
on	O
the	O
specific	O
transport	O
mechanism	O
of	O
the	O
network	O
to	O
which	O
the	O
receiver	O
is	O
connected	O
.	O
</s>
<s>
The	O
second	O
structure	O
involved	O
in	O
the	O
location	O
resolution	O
process	O
is	O
a	O
proper	O
resolution	O
table	O
which	O
,	O
given	O
a	O
content	O
's	O
CRID	B-Device
,	O
returns	O
one	O
or	O
several	O
locators	O
that	O
enable	O
the	O
receiver	O
to	O
access	O
an	O
instance	O
of	O
that	O
content	O
,	O
or	O
one	O
or	O
many	O
CRIDs	B-Device
that	O
allow	O
it	O
to	O
move	O
forward	O
in	O
the	O
resolution	O
process	O
.	O
</s>
<s>
The	O
figure	O
shows	O
an	O
example	O
of	O
this	O
second	O
structure	O
,	O
an	O
XML	O
document	O
according	O
to	O
the	O
specifications	O
of	O
the	O
XML	O
Schema	O
defined	O
in	O
TV-Anytime	B-Device
.	O
</s>
<s>
The	O
first	O
one	O
declares	O
how	O
a	O
CRID	B-Device
(	O
crid://tv.com/Friends/all	O
)	O
,	O
which	O
corresponds	O
to	O
a	O
group	O
content	O
that	O
encompasses	O
several	O
episodes	O
(	O
two	O
)	O
of	O
the	O
“	O
Friends	O
”	O
series	O
is	O
resolved	O
.	O
</s>
<s>
The	O
result	O
of	O
the	O
resolution	O
process	O
provides	O
two	O
new	O
CRIDs	B-Device
each	O
of	O
them	O
corresponding	O
to	O
one	O
of	O
the	O
two	O
episodes	O
.	O
</s>
<s>
The	O
second	O
<Result>	O
element	O
resolves	O
the	O
CRID	B-Device
of	O
the	O
first	O
episode	O
of	O
the	O
first	O
season	O
.	O
</s>
<s>
The	O
“	O
acquire	O
”	O
attribute	O
with	O
“	O
any	O
”	O
value	O
indicates	O
that	O
any	O
of	O
them	O
are	O
good	O
(	O
the	O
second	O
one	O
is	O
a	O
repetition	O
broadcast	B-Operating_System
a	O
week	O
later	O
)	O
.	O
</s>
<s>
Once	O
the	O
user	O
has	O
selected	O
a	O
given	O
content	O
(	O
identified	O
by	O
the	O
corresponding	O
CRID	B-Device
)	O
to	O
perform	O
some	O
action	O
upon	O
it	O
,	O
the	O
receiver	O
begins	O
the	O
location	O
resolution	O
process	O
that	O
shall	O
lead	O
to	O
specific	O
location	O
information	O
that	O
allows	O
access	O
to	O
a	O
copy	O
of	O
the	O
content	O
.	O
</s>
<s>
It	O
is	O
possible	O
to	O
make	O
a	O
basic	O
distinction	O
between	O
unidirectional	B-Device
networks	I-Device
,	O
where	O
the	O
receiver	O
can	O
only	O
receive	O
information	O
through	O
the	O
broadcast	B-Operating_System
channel	O
,	O
and	O
bidirectional	O
networks	O
,	O
where	O
there	O
is	O
also	O
a	O
return	O
channel	O
through	O
which	O
the	O
receiver	O
can	O
communicate	O
with	O
the	O
outside	O
(	O
typically	O
an	O
Internet	O
access	O
)	O
.	O
</s>
<s>
For	O
receivers	O
connected	O
only	O
to	O
a	O
broadcast	B-Operating_System
channel	O
,	O
it	O
is	O
clear	O
that	O
the	O
resolution	O
information	O
must	O
come	O
directly	O
from	O
that	O
channel	O
,	O
or	O
be	O
available	O
somehow	O
in	O
an	O
existing	O
local	O
storage	O
system	O
.	O
</s>
<s>
After	O
selecting	O
a	O
CRID	B-Device
,	O
the	O
first	O
thing	O
the	O
receiver	O
needs	O
to	O
do	O
is	O
check	O
the	O
information	O
about	O
where	O
to	O
find	O
the	O
resolution	O
table	O
.	O
</s>
<s>
For	O
this	O
,	O
it	O
must	O
find	O
a	O
RAR	O
record	O
associated	O
with	O
the	O
authority	O
of	O
the	O
selected	O
CRID	B-Device
.	O
</s>
<s>
The	O
information	O
that	O
will	O
receive	O
through	O
that	O
access	O
point	O
will	O
consist	O
of	O
a	O
message	O
for	O
each	O
of	O
the	O
consulted	O
CRIDs	B-Device
(	O
for	O
example	O
,	O
a	O
<Result>	O
element	O
in	O
the	O
ContentReferencingTable	O
)	O
.	O
</s>
<s>
To	O
make	O
the	O
CRID	B-Device
even	O
more	O
globally	O
available	O
the	O
IETF	O
will	O
publish	O
a	O
request	O
for	O
comments	O
specifying	O
the	O
use	O
of	O
the	O
CRID	B-Device
over	O
the	O
web	O
.	O
</s>
<s>
This	O
will	O
allow	O
consumer	O
devices	O
to	O
hook	O
up	O
to	O
content	O
provider	O
servers	O
,	O
much	O
like	O
current	O
browsers	O
look	O
up	O
webservers	O
,	O
requesting	O
content	O
by	O
CRID	B-Device
.	O
</s>
<s>
The	O
long-term	O
goal	O
is	O
that	O
CRIDs	B-Device
should	O
be	O
available	O
for	O
use	O
by	O
cell	O
phones	O
,	O
PDAs	B-Application
,	O
digital	B-Application
TV	I-Application
receivers	O
and	O
other	O
consumer	O
devices	O
for	O
fetching	O
content	O
,	O
either	O
from	O
a	O
broadcast	B-Operating_System
stream	I-Operating_System
or	O
over	O
IP	B-Protocol
networks	I-Protocol
.	O
</s>
