<s>
An	O
abstracting	B-Library
service	I-Library
is	O
a	O
service	O
that	O
provides	O
abstracts	O
of	O
publications	O
,	O
often	O
on	O
a	O
subject	O
or	O
group	O
of	O
related	O
subjects	O
,	O
usually	O
on	O
a	O
subscription	O
basis	O
.	O
</s>
<s>
An	O
indexing	B-Library
service	I-Library
is	O
a	O
service	O
that	O
assigns	O
descriptors	O
and	O
other	O
kinds	O
of	O
access	O
points	O
to	O
documents	O
.	O
</s>
<s>
The	O
word	O
indexing	B-Library
service	I-Library
is	O
today	O
mostly	O
used	O
for	O
computer	O
programs	O
,	O
but	O
may	O
also	O
cover	O
services	O
providing	O
back-of-the-book	O
indexes	O
,	O
journal	O
indexes	O
,	O
and	O
related	O
kinds	O
of	O
indexes	O
.	O
</s>
<s>
An	O
indexing	B-Library
and	I-Library
abstracting	I-Library
service	I-Library
is	O
a	O
service	O
that	O
provides	O
shortening	O
or	O
summarizing	O
of	O
documents	O
and	O
assigning	O
of	O
descriptors	O
for	O
referencing	O
documents	O
.	O
</s>
<s>
The	O
product	O
is	O
often	O
an	O
abstracts	O
journal	O
or	O
a	O
bibliographic	B-Library
index	I-Library
,	O
which	O
may	O
be	O
a	O
subject	O
bibliography	O
or	O
a	O
bibliographic	B-Library
database	I-Library
.	O
</s>
<s>
Guidelines	O
for	O
indexing	B-Library
and	I-Library
abstracting	I-Library
,	O
including	O
the	O
evaluation	O
of	O
such	O
services	O
,	O
are	O
given	O
in	O
the	O
literature	O
of	O
library	O
and	O
information	O
science	O
.	O
</s>
