[Swift-user] Thoughts on a data dependency issues

Ben Clifford benc at hawaga.org.uk
Fri Feb 13 16:30:26 CST 2009

There's a similar situation when staging in applications in the way that 
Mats and I did for his sample application - if you have multiple 
architectures, and are staging in an application, then it would be nice to 
parameterise which file goes in by selected site.

That does really slightly wierd stuff with dependencies, though - the set 
of sites available for a particular job then depends on which intermediate 
files have been created, and perhaps introduces something like the 
non-deterministic dependencies that have been talked about before: compute 
these 7 files on 7 different sites, and then whichever one finishes first, 
use that.

> An interesting case/feature, perhaps, is some new swift option to say 
> dont transfer the file, just pass the filename, and send a uri (returned 
> by the mapper) that an app wrapper can fetch dynamically.

There is an 'extern' type for representing dependencies on data that is 
not managed by Swift. No mapping happens, and you get to move data round 
however you want. Performing your own staging from your own data store, 
for example by pulling something from a URI that you have constructed 
yourself, using your own application-side data retrieval mechanism seems a 
reasonable use case for 'extern'.

Beyond that, I don't know if any further support is needed from Swift - 
try it and see.


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