Jonas Johansson wrote:
Hi all,
A Composite Command is handled as a separate thread, but from reading
http://udig.refractions.net/confluence/display/DEV/5+Composite+Commands
it is unclear if subcommands are handled serially within the composite
command or not. Are they?
I think so, you must remember that commands are there to produce side
effects (almost like a mini procedural programming language).
I keep thinking of a "processing service" as a bit more functional - set
up the chain of WPS services and punt data in one end ...
I could however be completely out to lunch....
time
| composite command{
| subcommand1
| subcommand2 (2 hours)
| subcommand3
V }
I'm thinking that using a WPS as a operation could be performed as a
series of commands. Depending on the operation, the transfer of data
between client and WPS server could potentially be asynchronous and take
a long time. Lets say that the subcommand that would send the request to
the WPS and receive the results takes 2 hours to complete. I would need
this subcommand to complete before I do some later commands on the
results. Is this so?
I see where you are going, and it does make sense. You need some actual
infrastructure to "chain" your things together, the command pattern is
suitable when working in chunks of processing like that.
Let me try to explain my other idea - set up a chain of:
- fetch features
- buffer features
- renderer features to image
- convolve image
The idea being that each feature could make the entire trip from start
to finish - before the next one.
And because I am thinking like a functional language I can do tricks
like divide my query into
two (one for each processor).
Incidentally I saw this bug and thought of you:
- http://jira.codehaus.org/browse/GEOT-153
Something to think about when we figure it out.
Jody
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