Hi Jean-Luc - OSLC Core considered this a while back and there was no consensus. Issues such as what status code, Location headers and resources you return when some creates succeed and others fail were part of the discussion. Multiple POSTs did not seem to be a showstopper for current consumers. I don't think OSLC Core has revisited this. See the thread titled "Creating multiple resources in one POST" here:
http://open-services.net/pipermail/oslc-core_open-services.net/2011-October/thread.html
Having said that, I think it might be possible to create JAX-RS POST methods which accept an array (or collection) of OSLC resources and create them. I've never tested anything like this in OSLC4J, but there is a slim (!) chance it might work today. However, the OSLC4J JAX-RS providers would likely have to be updated to support this (even if experimentally). I suggest opening an enhancement request here:
https://bugs.eclipse.org/bugs/enter_bug.cgi?product=Lyo if you want to pursue this.
Regards,
Mike