<s>
Z-Push	B-Protocol
(	O
presumably	O
Z	O
is	O
for	O
Zarafa	B-Protocol
)	O
is	O
a	O
FOSS	B-Application
implementation	O
of	O
the	O
Microsoft	B-Protocol
Exchange	I-Protocol
ActiveSync	I-Protocol
protocol	O
which	O
is	O
used	O
to	O
synchronize	O
email	O
,	O
personal	O
contacts	O
and	O
other	O
items	O
between	O
a	O
central	O
server	O
and	O
a	O
mobile	O
device	O
.	O
</s>
<s>
Z-Push	B-Protocol
enables	O
any	O
PHP-based	O
groupware	B-Application
package	O
to	O
become	O
fully	O
sync	O
able	O
with	O
any	O
ActiveSync-compliant	O
device	O
.	O
</s>
<s>
Currently	O
,	O
Z-Push	B-Protocol
includes	O
four	O
backends	O
:	O
the	O
IMAP	B-Protocol
and	O
the	O
Maildir	O
backend	O
for	O
e-mail	O
synchronization	O
,	O
the	O
vCard	O
backend	O
for	O
contact	O
synchronization	O
and	O
one	O
for	O
the	O
Zarafa	B-Protocol
package	O
which	O
is	O
sold	O
by	O
allowing	O
full	O
synchronization	O
of	O
E-mail	O
,	O
Calendar	O
,	O
Contacts	O
,	O
and	O
Tasks	O
.	O
</s>
<s>
There	O
is	O
also	O
a	O
3rd	O
party	O
project	O
that	O
implements	O
a	O
Zimbra	B-Protocol
Backend	O
,	O
allowing	O
Z-push	B-Protocol
to	O
be	O
used	O
with	O
a	O
ZCS	O
server	O
(	O
Including	O
opensource	O
edition	O
)	O
.	O
</s>
<s>
With	O
the	O
optional	O
Kopano	O
Outlook	O
Extension	O
(	O
available	O
only	O
for	O
paid	O
subscribers	O
of	O
Zarafa/Kopano	O
)	O
,	O
additional	O
Outlook	O
features	O
are	O
enabled	O
such	O
as	O
Out	O
of	O
Office	O
replies	O
,	O
Notes	O
synchronization	O
,	O
opening	O
of	O
shared	O
and	O
public	O
folders	O
and	O
synchronization	O
of	O
the	O
Global	O
Address	O
Book	O
.	O
</s>
<s>
The	O
future	O
sustainability	O
of	O
the	O
Z-Push	B-Protocol
project	O
is	O
in	O
question	O
after	O
Kopano	O
(	O
formerly	O
Zarafa	B-Protocol
)	O
announced	O
that	O
they	O
would	O
no	O
longer	O
be	O
supporting	O
the	O
project	O
.	O
</s>
<s>
The	O
Z-Push	B-Protocol
protocol	O
is	O
HTTP	O
based	O
,	O
and	O
uses	O
WBXML	B-Protocol
(	O
WAP	O
Binary	O
XML	B-Protocol
)	O
as	O
a	O
communication	O
layer	O
,	O
which	O
is	O
used	O
for	O
bi-directional	O
communication	O
between	O
the	O
PDA/cellular	O
phone	O
and	O
the	O
Server	O
.	O
</s>
<s>
The	O
Z-Push	B-Protocol
hides	O
the	O
complexity	O
of	O
handling	O
these	O
protocol	O
requests	O
to	O
the	O
backend	O
developer	O
,	O
who	O
only	O
needs	O
to	O
implement	O
various	O
standard	O
functions	O
,	O
like	O
getting	O
a	O
list	O
of	O
items	O
,	O
and	O
getting	O
the	O
data	O
for	O
a	O
specific	O
item	O
.	O
</s>
<s>
All	O
that	O
is	O
needed	O
is	O
a	O
good	O
understanding	O
of	O
the	O
WBXML	B-Protocol
object	O
definitions	O
and	O
fields	O
,	O
and	O
a	O
developer	O
can	O
quite	O
easily	O
get	O
the	O
items	O
of	O
any	O
groupware	B-Application
solutions	O
onto	O
the	O
PDA/cellular	O
phone	O
.	O
</s>
<s>
The	O
Z-Push	B-Protocol
has	O
various	O
performance	O
and	O
usability-related	O
features	O
;	O
for	O
example	O
,	O
the	O
entire	O
architecture	O
of	O
the	O
project	O
is	O
based	O
on	O
the	O
idea	O
that	O
only	O
one	O
message	O
should	O
ever	O
have	O
to	O
be	O
in	O
memory	O
at	O
one	O
time	O
,	O
even	O
when	O
the	O
server	O
is	O
sending	O
hundreds	O
of	O
messages	O
to	O
a	O
PDA	O
.	O
</s>
<s>
This	O
may	O
sound	O
easy	O
,	O
but	O
in	O
most	O
XML-based	O
applications	O
,	O
the	O
XML	B-Protocol
result	O
data	O
is	O
built	O
in-memory	O
before	O
being	O
serialized	O
to	O
the	O
network	O
,	O
exactly	O
the	O
opposite	O
to	O
what	O
Z-Push	B-Protocol
does	O
,	O
as	O
data	O
is	O
streamed	O
to	O
the	O
client	O
while	O
it	O
is	O
read	O
from	O
the	O
backend	O
.	O
</s>
<s>
This	O
not	O
only	O
improves	O
already	O
restricted	O
memory	O
usage	O
in	O
PHP	B-Application
,	O
it	O
also	O
makes	O
the	O
progress	O
bar	O
on	O
the	O
client	O
more	O
user-friendly	O
,	O
as	O
data	O
starts	O
arriving	O
as	O
soon	O
as	O
the	O
synchronization	O
request	O
is	O
made	O
.	O
</s>
<s>
Z-Push	B-Protocol
has	O
provided	O
a	O
streaming	O
WBXML	B-Protocol
encoder	O
and	O
decoder	O
to	O
make	O
this	O
happen	O
.	O
</s>
<s>
When	O
a	O
backend	O
supports	O
it	O
,	O
Z-Push	B-Protocol
can	O
also	O
make	O
use	O
of	O
advanced	O
features	O
which	O
bring	O
server	O
load	O
down	O
even	O
lower	O
,	O
for	O
example	O
reading	O
message	O
changes	O
directly	O
from	O
a	O
'	O
diff	O
 '	O
source	O
,	O
instead	O
of	O
comparing	O
all	O
the	O
messages	O
with	O
whatever	O
was	O
in	O
their	O
last	O
time	O
.	O
</s>
<s>
So	O
if	O
the	O
groupware	B-Application
backend	O
can	O
provide	O
a	O
list	O
of	O
changes	O
on-the-fly	O
,	O
then	O
Z-Push	B-Protocol
can	O
use	O
this	O
information	O
almost	O
instantaneously	O
.	O
</s>
<s>
Zarafa	B-Protocol
provides	O
an	O
incremental	O
synchronization	O
backend	O
for	O
its	O
own	O
MAPI-based	O
solution	O
here	O
through	O
their	O
PHP-MAPI	O
extension	O
,	O
enabling	O
extremely	O
low-load	O
synchronizations	O
.	O
</s>
