<s>
EXPRESS	O
is	O
a	O
standard	O
data	B-Language
modeling	I-Language
language	I-Language
for	O
product	O
data	O
.	O
</s>
<s>
EXPRESS	O
is	O
formalized	O
in	O
the	O
ISO	O
Standard	O
for	O
the	O
Exchange	O
of	O
Product	O
model	O
STEP	O
(	O
ISO	O
10303	O
)	O
,	O
and	O
standardized	O
as	O
ISO	B-Application
10303-11	I-Application
.	O
</s>
<s>
Data	B-Application
models	I-Application
formally	O
define	O
data	O
objects	O
and	O
relationships	O
among	O
data	O
objects	O
for	O
a	O
domain	O
of	O
interest	O
.	O
</s>
<s>
Some	O
typical	O
applications	O
of	O
data	B-Application
models	I-Application
include	O
supporting	O
the	O
development	O
of	O
databases	O
and	O
enabling	O
the	O
exchange	O
of	O
data	O
for	O
a	O
particular	O
area	O
of	O
interest	O
.	O
</s>
<s>
Data	B-Application
models	I-Application
are	O
specified	O
in	O
a	O
data	B-Language
modeling	I-Language
language	I-Language
.	O
</s>
<s>
EXPRESS	O
is	O
a	O
data	B-Language
modeling	I-Language
language	I-Language
defined	O
in	O
ISO	B-Application
10303-11	I-Application
,	O
the	O
EXPRESS	O
Language	B-Language
Reference	O
Manual	O
.	O
</s>
<s>
An	O
EXPRESS	O
data	B-Application
model	I-Application
can	O
be	O
defined	O
in	O
two	O
ways	O
,	O
textually	O
and	O
graphically	O
.	O
</s>
<s>
For	O
formal	O
verification	O
and	O
as	O
input	O
for	O
tools	O
such	O
as	O
SDAI	B-Application
the	O
textual	O
representation	O
within	O
an	O
ASCII	B-Protocol
file	I-Protocol
is	O
the	O
most	O
important	O
one	O
.	O
</s>
<s>
EXPRESS	O
is	O
similar	O
to	O
programming	O
languages	O
such	O
as	O
Pascal	B-Application
.	O
</s>
<s>
EXPRESS-G	O
is	O
a	O
standard	O
graphical	O
notation	O
for	O
information	B-Application
models	I-Application
.	O
</s>
<s>
It	O
is	O
a	O
companion	O
to	O
the	O
EXPRESS	O
language	B-Language
for	O
displaying	O
entity	O
and	O
type	O
definitions	O
,	O
relationships	O
and	O
cardinality	O
.	O
</s>
<s>
This	O
graphical	O
notation	O
supports	O
a	O
subset	O
of	O
the	O
EXPRESS	O
language	B-Language
.	O
</s>
<s>
One	O
of	O
the	O
advantages	O
of	O
using	O
EXPRESS-G	O
over	O
EXPRESS	O
is	O
that	O
the	O
structure	O
of	O
a	O
data	B-Application
model	I-Application
can	O
be	O
presented	O
in	O
a	O
more	O
understandable	O
manner	O
.	O
</s>
<s>
The	O
data	B-Application
model	I-Application
presented	O
in	O
figure	O
could	O
be	O
used	O
to	O
specify	O
the	O
requirements	O
of	O
a	O
database	O
for	O
an	O
audio	O
compact	O
disc	O
(	O
CD	O
)	O
collection	O
.	O
</s>
<s>
A	O
simple	O
EXPRESS	O
data	B-Application
model	I-Application
looks	O
like	O
fig	O
2	O
,	O
and	O
the	O
code	O
like	O
this	O
:	O
</s>
<s>
The	O
data	B-Application
model	I-Application
is	O
enclosed	O
within	O
the	O
EXPRESS	O
schema	O
Family	O
.	O
</s>
<s>
An	O
entity	O
can	O
be	O
defined	O
to	O
be	O
a	O
subtype	O
of	O
one	O
or	O
several	O
other	O
entities	O
(	O
multiple	B-Application
inheritance	I-Application
is	O
allowed	O
!	O
)	O
.	O
</s>
<s>
The	O
functions	O
and	O
procedures	O
allow	O
formulating	O
complex	O
statements	O
with	O
local	O
variables	O
,	O
parameters	O
and	O
constants	O
-	O
very	O
similar	O
to	O
a	O
programming	O
language	B-Language
.	O
</s>
<s>
The	O
EXPRESS	O
language	B-Language
can	O
describe	O
local	O
and	O
global	O
rules	O
.	O
</s>
