<s>
ERIL	B-Application
(	O
Entity-Relationship	B-Architecture
and	O
Inheritance	O
Language	O
)	O
is	O
a	O
visual	O
language	O
for	O
representing	O
the	O
data	O
structure	O
of	O
a	O
computer	O
system	O
.	O
</s>
<s>
As	O
its	O
name	O
suggests	O
,	O
ERIL	B-Application
is	O
based	O
on	O
entity-relationship	B-Architecture
diagrams	I-Architecture
and	O
class	O
diagrams	O
.	O
</s>
<s>
ERIL	B-Application
combines	O
the	O
relational	B-Architecture
and	O
object-oriented	B-Language
approaches	O
to	O
data	O
modeling	O
.	O
</s>
<s>
ERIL	B-Application
can	O
be	O
seen	O
as	O
a	O
set	O
of	O
guidelines	O
aimed	O
at	O
improving	O
the	O
readability	O
of	O
structure	B-Language
diagrams	I-Language
.	O
</s>
<s>
These	O
guidelines	O
were	O
borrowed	O
from	O
DRAKON	B-Language
,	O
a	O
variant	O
of	O
flowcharts	B-Language
created	O
within	O
the	O
Russian	O
space	O
program	O
.	O
</s>
<s>
ERIL	B-Application
itself	O
was	O
developed	O
by	O
Stepan	O
Mitkin	O
.	O
</s>
<s>
The	O
ERIL	B-Application
guidelines	O
for	O
drawing	O
diagrams	O
:	O
</s>
<s>
Vertical	O
lines	O
mean	O
ownership	O
(	O
composition	B-Language
)	O
.	O
</s>
<s>
It	O
is	O
not	O
recommended	O
to	O
fit	O
the	O
whole	O
data	B-Application
model	I-Application
on	O
a	O
single	O
diagram	O
.	O
</s>
<s>
A	O
class	O
(	O
table	O
)	O
in	O
ERIL	B-Application
can	O
have	O
several	O
indexes	O
.	O
</s>
<s>
Each	O
index	O
in	O
ERIL	B-Application
can	O
include	O
one	O
or	O
more	O
fields	O
,	O
similar	O
to	O
indexes	O
in	O
relational	B-Application
databases	I-Application
.	O
</s>
<s>
ERIL	B-Application
indexes	O
are	O
logical	O
.	O
</s>
<s>
Links	O
between	O
classes	O
(	O
tables	O
)	O
in	O
ERIL	B-Application
are	O
implemented	O
by	O
the	O
so-called	O
"	O
link	O
"	O
fields	O
.	O
</s>
<s>
ERIL	B-Application
is	O
supposed	O
to	O
model	O
any	O
kind	O
of	O
data	O
regardless	O
of	O
the	O
storage	O
.	O
</s>
<s>
The	O
same	O
ERIL	B-Application
diagram	O
can	O
represent	O
data	O
stored	O
in	O
a	O
relational	B-Application
database	I-Application
,	O
in	O
a	O
NoSQL	B-General_Concept
database	O
,	O
XML	B-Protocol
file	O
or	O
in	O
the	O
memory	O
.	O
</s>
<s>
ERIL	B-Application
diagrams	O
serve	O
two	O
purposes	O
.	O
</s>
<s>
Code	O
that	O
can	O
be	O
generated	O
includes	O
specialized	O
collection	O
classes	O
,	O
hash	O
and	O
comparison	O
functions	O
,	O
data	O
retrieval	O
and	O
modification	O
procedures	O
,	O
SQL	B-Language
data-definition	I-Language
code	O
,	O
etc	O
.	O
</s>
<s>
Code	O
generated	O
from	O
ERIL	B-Application
diagrams	O
can	O
ensure	O
referential	O
and	O
uniqueness	O
data	O
integrity	O
.	O
</s>
<s>
In	O
some	O
ways	O
ERIL	B-Application
can	O
be	O
compared	O
to	O
object-relational	B-General_Concept
mapping	I-General_Concept
frameworks	O
.	O
</s>
