<s>
Core	B-Application
Data	I-Application
is	O
an	O
object	B-Application
graph	I-Application
and	O
persistence	B-Library
framework	I-Library
provided	O
by	O
Apple	O
in	O
the	O
macOS	B-Operating_System
and	O
iOS	B-Operating_System
operating	B-General_Concept
systems	I-General_Concept
.	O
</s>
<s>
It	O
was	O
introduced	O
in	O
Mac	B-Application
OS	I-Application
X	I-Application
10.4	I-Application
Tiger	I-Application
and	O
iOS	B-Operating_System
with	O
iPhone	O
SDK	O
3.0	O
.	O
</s>
<s>
It	O
allows	O
data	O
organized	O
by	O
the	O
relational	B-General_Concept
entity	I-General_Concept
–	I-General_Concept
attribute	I-General_Concept
model	I-General_Concept
to	O
be	O
serialized	B-Application
into	O
XML	B-Protocol
,	O
binary	O
,	O
or	O
SQLite	B-Language
stores	O
.	O
</s>
<s>
Core	B-Application
Data	I-Application
manages	O
the	O
serialized	B-Application
version	O
,	O
providing	O
object	O
lifecycle	O
and	O
object	B-Application
graph	I-Application
management	O
,	O
including	O
persistence	B-Application
.	O
</s>
<s>
Core	B-Application
Data	I-Application
interfaces	O
directly	O
with	O
SQLite	B-Language
,	O
insulating	O
the	O
developer	O
from	O
the	O
underlying	O
SQL	B-Language
.	O
</s>
<s>
Just	O
as	O
Cocoa	B-Operating_System
Bindings	I-Operating_System
handle	O
many	O
of	O
the	O
duties	O
of	O
the	O
controller	O
in	O
a	O
model	O
–	O
view	O
–	O
controller	O
design	O
,	O
Core	B-Application
Data	I-Application
handles	O
many	O
of	O
the	O
duties	O
of	O
the	O
data	O
model	O
.	O
</s>
<s>
Among	O
other	O
tasks	O
,	O
it	O
handles	O
change	O
management	O
,	O
serializing	B-Application
to	O
disk	O
,	O
memory	O
footprint	O
minimization	O
and	O
queries	O
against	O
the	O
data	O
.	O
</s>
<s>
Core	B-Application
Data	I-Application
describes	O
data	O
with	O
a	O
high	O
level	O
data	O
model	O
expressed	O
in	O
terms	O
of	O
entities	O
and	O
their	O
relationships	O
plus	O
fetch	O
requests	O
that	O
retrieve	O
entities	O
meeting	O
specific	O
criteria	O
.	O
</s>
<s>
When	O
combined	O
with	O
Cocoa	B-Operating_System
bindings	I-Operating_System
the	O
UI	O
can	O
display	O
many	O
components	O
of	O
the	O
data	O
model	O
without	O
needing	O
background	O
code	O
.	O
</s>
<s>
In	O
order	O
to	O
manage	O
these	O
,	O
the	O
author	O
intends	O
to	O
read	O
the	O
vCards	O
into	O
objects	O
,	O
and	O
then	O
store	O
them	O
in	O
a	O
single	O
larger	O
XML	B-Protocol
file	O
.	O
</s>
<s>
Using	O
Core	B-Application
Data	I-Application
the	O
developer	O
would	O
drag	O
their	O
schema	B-Application
from	O
the	O
data	O
designer	O
in	O
Xcode	B-Operating_System
into	O
an	O
interface	O
builder	O
window	O
to	O
create	O
a	O
GUI	O
for	O
their	O
schema	B-Application
.	O
</s>
<s>
They	O
could	O
then	O
write	O
standard	O
Objective-C	B-Language
or	O
Swift	B-Application
code	O
to	O
read	O
vCard	O
files	O
and	O
put	O
the	O
data	O
into	O
Core	B-Application
Data	I-Application
managed	O
entities	O
.	O
</s>
<s>
From	O
that	O
point	O
on	O
the	O
author	O
's	O
code	O
manipulates	O
these	O
Core	B-Application
Data	I-Application
objects	O
,	O
rather	O
than	O
the	O
underlying	O
vCards	O
.	O
</s>
<s>
Connecting	O
the	O
Save	O
menu	O
item	O
to	O
the	O
appropriate	O
method	O
in	O
the	O
controller	O
object	O
will	O
direct	O
the	O
controller	O
to	O
examine	O
the	O
object	O
stack	O
,	O
determine	O
which	O
objects	O
are	O
dirty	O
,	O
and	O
then	O
re-write	O
a	O
Core	B-Application
Data	I-Application
document	O
file	O
with	O
these	O
changes	O
.	O
</s>
<s>
Core	B-Application
Data	I-Application
is	O
organized	O
into	O
a	O
large	O
hierarchy	O
of	O
classes	O
,	O
though	O
interaction	O
is	O
only	O
prevalent	O
with	O
a	O
small	O
set	O
of	O
them	O
.	O
</s>
<s>
Core	B-Application
Data	I-Application
can	O
serialize	B-Application
objects	O
into	O
XML	B-Protocol
,	O
binary	O
,	O
or	O
SQLite	B-Language
for	O
storage	O
.	O
</s>
<s>
With	O
the	O
release	O
of	O
Mac	B-Application
OS	I-Application
X	I-Application
10.5	I-Application
Leopard	I-Application
,	O
developers	O
can	O
also	O
create	O
their	O
own	O
custom	O
atomic	B-General_Concept
store	O
types	O
.	O
</s>
<s>
Each	O
method	O
carries	O
advantages	O
and	O
disadvantages	O
,	O
such	O
as	O
being	O
human	O
readable	O
(	O
XML	B-Protocol
)	O
or	O
more	O
memory	O
efficient	O
(	O
SQLite	B-Language
)	O
.	O
</s>
<s>
This	O
portion	O
of	O
Core	B-Application
Data	I-Application
is	O
similar	O
to	O
the	O
original	O
Enterprise	B-General_Concept
Objects	I-General_Concept
Framework	I-General_Concept
(	O
EOF	O
)	O
system	O
,	O
in	O
that	O
one	O
can	O
write	O
fairly	O
sophisticated	O
queries	O
.	O
</s>
<s>
Unlike	O
EOF	O
,	O
it	O
is	O
not	O
possible	O
to	O
write	O
your	O
own	O
SQL	B-Language
,	O
as	O
the	O
underlying	O
store	O
may	O
not	O
be	O
SQL-based	O
.	O
</s>
<s>
Recently	O
,	O
Core	B-Application
Data	I-Application
store	O
for	O
ODBC	O
has	O
been	O
made	O
available	O
in	O
ODBC	O
framework	O
.	O
</s>
<s>
Core	B-Application
Data	I-Application
schemas	B-Application
are	O
standardized	O
.	O
</s>
<s>
If	O
you	O
have	O
the	O
Xcode	B-Operating_System
Data	O
Model	O
file	O
,	O
you	O
can	O
read	O
and	O
write	O
files	O
in	O
that	O
format	O
freely	O
.	O
</s>
<s>
Unlike	O
EOF	O
,	O
though	O
,	O
Core	B-Application
Data	I-Application
is	O
not	O
currently	O
designed	O
for	O
multiuser	O
or	O
simultaneous	O
access	O
unless	O
you	O
use	O
ODBC	O
framework	O
.	O
</s>
<s>
Schema	B-Application
migration	O
is	O
also	O
non-trivial	O
,	O
almost	O
always	O
requiring	O
code	O
.	O
</s>
<s>
If	O
other	O
developers	O
have	O
access	O
to	O
and	O
depend	O
upon	O
your	O
data	O
model	O
,	O
you	O
may	O
need	O
to	O
provide	O
version	O
translation	O
code	O
in	O
addition	O
to	O
a	O
new	O
data	O
model	O
if	O
your	O
schema	B-Application
changes	O
.	O
</s>
<s>
Core	B-Application
Data	I-Application
owes	O
much	O
of	O
its	O
design	O
to	O
an	O
earlier	O
NeXT	O
product	O
,	O
Enterprise	B-General_Concept
Objects	I-General_Concept
Framework	I-General_Concept
(	O
EOF	O
)	O
.	O
</s>
<s>
EOF	O
was	O
an	O
object-relational	B-General_Concept
mapping	I-General_Concept
for	O
high-end	O
SQL	B-Language
database	I-Language
engines	O
such	O
as	O
Microsoft	B-Application
SQL	I-Application
Server	I-Application
and	O
Oracle	B-General_Concept
.	O
</s>
<s>
Throughout	O
its	O
history	O
,	O
EOF	O
contained	O
a	O
number	O
of	O
bits	O
of	O
useful	O
code	O
that	O
were	O
not	O
otherwise	O
available	O
under	O
NeXTSTEP/OpenStep	O
.	O
</s>
<s>
Many	O
developers	O
complained	O
that	O
this	O
state	O
management	O
code	O
was	O
far	O
too	O
useful	O
to	O
be	O
isolated	O
in	O
EOF	O
,	O
and	O
it	O
was	O
later	O
moved	O
into	O
the	O
Cocoa	B-Operating_System
API	I-Operating_System
during	O
the	O
transition	O
to	O
Mac	B-Operating_System
OS	I-Operating_System
X	I-Operating_System
.	O
</s>
<s>
EOF	O
was	O
used	O
primarily	O
along	O
with	O
another	O
OpenStep-era	O
product	O
,	O
WebObjects	B-Language
,	O
which	O
was	O
an	O
application	B-Application
server	I-Application
originally	O
based	O
on	O
Objective-C	B-Language
.	O
At	O
the	O
time	O
,	O
Apple	O
was	O
in	O
the	O
process	O
of	O
porting	O
WebObjects	B-Language
to	O
the	O
Java	B-Language
programming	I-Language
language	I-Language
,	O
and	O
as	O
part	O
of	O
this	O
conversion	O
,	O
EOF	O
became	O
much	O
more	O
difficult	O
to	O
use	O
from	O
Cocoa	B-Operating_System
.	O
</s>
<s>
It	O
is	O
this	O
concept	O
that	O
forms	O
the	O
basis	O
of	O
Core	B-Application
Data	I-Application
.	O
</s>
