<s>
Implicit	B-Architecture
invocation	I-Architecture
is	O
a	O
term	O
used	O
by	O
some	O
authors	O
for	O
a	O
style	O
of	O
software	B-Architecture
architecture	I-Architecture
in	O
which	O
a	O
system	O
is	O
structured	O
around	O
event	O
handling	O
,	O
using	O
a	O
form	O
of	O
callback	O
.	O
</s>
<s>
It	O
is	O
closely	O
related	O
to	O
inversion	B-Language
of	I-Language
control	I-Language
and	O
what	O
is	O
known	O
informally	O
as	O
the	B-Language
Hollywood	I-Language
principle	I-Language
.	O
</s>
<s>
Implicit	B-Architecture
invocation	I-Architecture
is	O
the	O
core	O
technique	O
behind	O
the	O
observer	B-Language
pattern	I-Language
.	O
</s>
