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Subject: Re: ObserverActivity

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From: Enrique Díez García (ediez@infomed.dia.fi.upm.es)
Date: Jun 02, 2008 09:02

Hi Mike,

I tell you our problem.

We have a code which executes two activities, activity A and activity B:

The activity A creates a perform document and sends it to the activity B.

The B activity uploads two files into a GRID repository with an
identifier in a file.

When the activity ends B (it should notify to the activity A that it has
already finished), the activity A picks up the identifier that uploaded
activity B and operates with it.

The problem is that the activity B "ends" sooner than we would like,
that is, the activity A continues executing its code before the activity
B ends, and therefore the activity A code is unable to recover this
identifier, because it still does not know it!

We want to wait for the identifier is ready, that is, we need the
activity A "wait" for the activity B is completed before continue running.

We tested waiting for the activity B "is complete," watching the
activity B´s state, but the B activity is never complete, the state
output of the activity B is always PROCESSING.

So we thought in ObserverActivity to wait for activity B.

Can you help us?

Thanks a lot!

  Enrique.

Mike Jackson escribió:
>
> Hi Enrique,
>
> I had a look at the ObserverActivity source code - it was in OGSA-DAI
> 2.2 source distributions:
>
> src/java/core/uk/org/ogsadai/activity/ObserverActivity.java
>
> It is an internal activity inserted by the 2.2 activity framework and
> used incases where an activity has an external output - that is, an
> output that is unconnected and so is exposed as an OGSA-DAI 2.2 output
> stream (and can be used with the 2.2 data transport operations).
>
> Unlike most activities, they don't take data in and/or put data out
> but rather "wrap" another activity and complete only when the wrapped
> activity enters a finished state. They weren't intended to be
> explicity inserted by clients in their workflows - and there's no way
> the workflow structure allows such a relationship between activities
> to be expressed. It could be argued that ObserverActivity is not an
> activity at all in the traditional sense of an OGSA-DAI activity but
> rather an ActivityObserver. This is why there is no XML Schema or
> client stub for this.
>
> What do you mean by "control the end of an activity execution"?
> Perhaps there's another way this can be realized.
>
> Cheers,
>
> mike
>
> On Thu, 29 May 2008, Enrique Díez García wrote:
>
>> I need to control the end of an activity execution, so I looked for
>> a solution and I found the ObserverActivity could be a solution for me.
>>
>> In
>>
>> http://www.ogsadai.org/documentation/ogsadai-wsrf-2.2/doc/api-docs/uk/org/ogsadai/activity/ObserverActivity.html
>>
>> it is said ObserverActivity was made by the OGSA-DAI Project Team,
>> but I´m searching the ObserverActivity xsd schema and de
>> ObserverActivity Java class but I have not found them.
>>
>>
>>
>> Where can I download them?
>>
>> How can I get them?
>>
>>
>>
>> Thanks,
>>
>> Enrique.
>>
>
> -------------------------------------------------------------------
> Dr. Michael (Mike) Jackson Tel: +(44)-0131-650-5141
> E-mail: m.jackson@epcc.ed.ac.uk Fax: +(44)-0131-650-6555
> EPCC OGSA-DAI Project
> WWW: http://www.epcc.ed.ac.uk WWW: http://www.ogsadai.org.uk
>
> The University of Edinburgh is a charitable body, registered in
> Scotland, with registration number SC005336.

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