[seek-dev] EcoGrid Query Service: Instances and Factories

Matt Jones jones at nceas.ucsb.edu
Tue Jan 20 17:09:31 PST 2004

EcoGrid team,

I've been working on the registry issues, and have run into some issues 
with the way Jing and Bing are using the Grid "Factory" pattern.  As 
they have implmented it, each wrapped server (like a metacat or srb) 
exposes a "Factory" which has a "createInstance" method.  When called, a 
new endpoint is created that exposes the methods in our 
EcoGridQeuryLevelOne interface spec.  This endpoint is then queried by 
only that one client.  However, this pattern makes it very hard for us 
to discover where the EcoGridQueryLevelOne services reside, because they 
don't exist at the time that the client is querying the registry.

I don't see what we gain from using the factory pattern here at all 
(given our underlying server systems), so I am proposing we eliminate 
use of Factories and just stick to EcoGridQueryLevelOne instances.  I 
think that doing so would substnatially simplify the demands on clients 
in the service discovery pahse while clients are querying the registry. 
  The details aof how I arrived at that proposal with Jing are in the 
attached IRC conversation.

Please review this information and let me know if you think it is a good 
idea to eliminate the use of factories.  Thanks,


PS We're on a tight time schedule, so prompt feedback is appreciated.
Matt Jones                                     jones at nceas.ucsb.edu
http://www.nceas.ucsb.edu/    Fax: 425-920-2439    Ph: 907-789-0496
National Center for Ecological Analysis and Synthesis (NCEAS)
University of California Santa Barbara
Interested in ecological informatics? http://www.ecoinformatics.org
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