Re: [Openflow-dev] Openflow and Event Channel

[kapil t. <kth...@ea...>]

hi julian,

i'm not sure i follow you.

in terms of hooking up workflow to event channel. yes it can be done quit=
e=20
easily. in my understanding (which i admit is still limited) basically th=
e=20
'application' which performs the transition can operate in automatic mode=
,=20
this application can then be a publisher of an event on the event channel=
,=20
notifying interested objects of the change, or alternatively it can be a=20
listener (in which case another 'application' should publish on the chann=
el).=20

in terms of communicating remotely, the event channel does not do anythin=
g=20
directly to facilitate this. an object which is listening for a particula=
r=20
event type can act as a proxy to an external entity. so in your example t=
he=20
local workflow can call the token move method, which in turn would publis=
h an=20
event, which in turn would be listened to by a proxy object, which in tur=
n=20
would communicate remotely with the remote server.

additionally there are complications if you want to maintain transactiona=
lly=20
integretity with the remote system. transactional communication between t=
wo=20
independent zope servers is also problematic, as xml-rpc triggers a reque=
st=20
which would be committed on the remote server, and the local server might=
 at=20
a latter point abort. while such communication could be worked, its *much=
*=20
easier if you desire transactional communication to synchronize on an=20
external resource like an rdbms.

in summary i'm not sure that the event channel combined with the workflow=
 has=20
much utility unless you need to notify several objects of a transition, o=
r=20
you intend component integration via using the event publication as an=20
integration point.

-kapil thangavelu


On Thursday 28 February 2002 04:57 am, Juli=E1n Mu=F1oz wrote:
> Kapil,
>
> In zope.org is published your new product "Event Channel".
>
> One thing I have done with Openflow is having two workflows in diferent=
s
> machines (Call them "Remote" and "Local").
>
> At one point, in the Client y fetch some objects in the Remote Server,
> each of this objects corresponding to a "Token" (which is now called a
> "Process Instance"), and then I create another Process Instance in the
> Local workflow.
>
> After some processing, In the local workflow, I launch the "Token.move"
> method in the remote workflow from the local workflow (I finish the rem=
ote
> activity or "workitem" in the new jargon). This is done with xml-rpc ov=
er
> ssh.
>
>
>
> I am thinking:
>
> Could be an activity a receiving channel waiting for a remote signal ?
> Could be this signal a remote workitem (with the information associated
> with it)
>
> Could be an activity a sending channel ?
>
>
>
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